1. Introduction

Pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. Chronic pain is pain that persists or recurs for longer than 3 months. Chronic pain is multifactorial: biological, psychological, and social factors contribute to the pain syndrome” [1].

This is how the International Classification of Diseases (ICD) 11 defines chronic pain. While International Classification of Diseases 10 did not provide a systematic categorization, leading to undefined treatment pathways due to the lack of classification codes, the International Association for the Study of Pain and the World Health Organization agreed to classify chronic pain into seven categories for the subsequent edition [2, 3].

People with chronic pain often suffer from anxiety, depression, sleep problems, and fatigue, which lead to limitations in work and personal life, as well as a reduced quality of life [4]. Pain is often measured using standardized instruments such as the Visual Analog Scale (VAS), the Numeric Rating Scale (NRS), or the Verbal Rating Scale (VRS) [5]. The McGill Pain Questionnaire  (MPQ) is also among these tools [6]. The VAS is a commonly used instrument for assessing pain intensity, where patients mark their pain sensation on a 100 mm line to evaluate therapies and changes in pain perception [7].

The NRS rates pain intensity from “no pain” to “worst imaginable pain” using numbers from 0 to 10 (sometimes also 0–20 or 0–100), where patients select the number that corresponds to their current pain level [8]. The VRS consists of a list of terms from which the patient selects or checks one [5]. The MPQ was the first to enable a multidimensional assessment of pain by considering intensity, emotional impact, and significance to the patient [9]. This led to the development of the Short Form, the MPQ-SF, which includes 15 descriptors (11 sensory, 4 affective), a VAS, and the Present Pain Intensity Index [10].

A study by Pain Alliance Europe from 2021 reported that 20 % of the population in Europe experiences chronic pain, with costs reaching into the hundreds of billions of euros [11]. Similar figures were reported in the United States in 2021, with 20.9 % of people suffering from chronic pain [12]. The costs are comparable to those in Europe [13].

Chronic pain can be treated with opioids as well as non-opioid pharmacologic treatments [14]. Another way to combat chronic pain is through the use of non-pharmacological treatments. This also includes the use of music interventions. A distinction is made between music therapy (MT) and music medicine. In MT, the patient works with a music therapist who designs a specific therapy. This can involve both actively creating or composing and listening to music [15]. There is also music medicine, where patients listen to music, usually through headphones, administered by medical staff without MT training. Depending on the situation, patients may have a say in what music is played [16]. Music interventions are cost-effective, have no side effects, and are non-discriminatory [17].

From a psychological perspective, music interventions are believed to increase motivation, improve mood, and alleviate pain by deliberately distracting from unpleasant sensations, thereby reducing the perception of pain or anxiety [17]. Pain processing in the brain involves multiple regions. Additionally, studies have shown that chronic pain is associated with altered brain function [18].

It was demonstrated, for instance, that various brain areas were active in people with osteoarthritis when experimentally induced acute pain was compared with clinical pain. Both pain states activated the pain matrix, but arthritic pain was associated with increased activity in the cingulate cortex, thalamus, and amygdala; these areas are involved in the processing of anxiety, emotions, and aversive conditioning [19]. Similarly, various brain areas are also activated during the processing of music [20]. The prefrontal cortex, which plays a key role in both pain and music processing, is involved in processes such as learning, memory, emotion regulation, and cognitive flexibility [17, 21, 22].

Systematic reviews on this topic have emerged in recent years. However, their methodology was limited, such as only searching for studies that involved vocal MT [23] or investigating the use of music interventions in older adults [24]. The aim of this review is to determine the effect of music on people with chronic pain. This review is the first to provide a comprehensive overview of this topic, thereby filling a research gap and generating new research opportunities.

Objectives

The aim of this systematic review was to determine and evaluate the effect of music interventions on individuals with chronic pain.

2. Methods

Criteria for considering studies for this review

The systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta- Analyses guidelines, as outlined in the PRISMA checklist [25].

Types of studies

Randomized controlled trials (RCTs) were included in the analysis, while quasi-randomized studies, cluster-randomized controlled trials, pilot studies, feasibility studies, and mixed methods studies were excluded. The studies could be either single- or double-blinded. Study designs with crossover or multi- arm trial approaches were also considered.

Types of participants

The review included studies conducted on adults diagnosed with chronic pain.

Types of intervention

The intervention included music-based interventions, while the control group received a placebo or no               therapy.The existing standard therapy was continued.

Electronic searches

The databases Cochrane Central Register of Controlled Trials and PubMed were searched. There were no restrictions on the time period or language. The search query was: chronic pain AND music* (see Appendix 1 for detailed search information). The “RCT” filter was activated in PubMed. The initial literature search was carried out from February 21 to February 26, 2024.

Searching other resources

 In addition to the electronic search, authors were also directly contacted for additional studies.

Data collection and analysis

Outcome

The primary outcome assessed in this review was the improvement of chronic pain without restrictions on the specific measurement methods used.

Selection of Studies

We conducted a thorough review of all titles and abstracts of studies identified through the search and those provided by the contacted authors. Studies that did not fulfill the inclusion criteria were excluded. Full-text analysis was carried out for the remaining studies, followed by a final decision on their suitability for inclusion in the review.

Data extraction and management

Data collection and analysis were performed using Review Manager 5. Information from each study was systematically recorded using data extraction forms, which captured details such as the first author, year of publication, study design, participants, interventions, outcomes, and ethical approval (refer to study characteristics in Appendix 2). Study selection and bias assessments were carried out by a single author, with any uncertainties resolved collaboratively through discussions among all authors.

Synthesis of Findings

When the inclusion criteria were satisfied, not all studies necessarily assessed every outcome. All identified outcomes were systematically analyzed and compared qualitatively across the studies. Missing data were documented in the bias assessment, including cases where authors were contacted but did not respond. Variability between studies was addressed by underscoring differences and offering detailed descriptions of the measurement methodologies employed.

Assessment of risk of bias in studies included

Each study included was assessed for any risk of bias using the Risk of Bias 2 tool [26]. A table was used to distinguish between a low, high, and unclear risk of bias.

The following items were evaluated:

1. Random sequence generation
2. Allocation concealment
3. Blinding of participants and personnel
4. Blinding of outcome assessment
5. Incomplete outcome data
6. Selective reporting
7. Other bias

3. Results

PubMed and Cochrane Central were searched for this review, yielding 279 articles (Figure 1). An additional 54 articles were obtained by contacting authors. After excluding 49 duplicates, 284 articles remained, with their titles and abstracts screened. A total of 266 articles were excluded because they        did not meet the criteria, the study was ongoing, or the article had been retracted. This left 18 articles, of which 4 more were excluded after full-text review for not meeting the criteria. A total of 14 studies were included in the review (see the study characteristics in Appendix 2). It should be noted that the study by Siedlecki (2009) is based on the work of Siedlecki and Good (2006). One study was exceptionally included because the intervention and control were reversed. Although the methodology would typically have required exclusion, it was considered because the control group only listened to music, while the intervention group additionally integrated tactile touch [27].

The age range of study participants ranged from 19 to 86, with some studies providing exact ages and others reporting the mean age with standard deviation. The studies were conducted in Turkey, China, France, Austria, Australia, the USA, Sweden, and Germany. The following chronic pain diagnoses were included in the studies: fibromyalgia, chronic pain, lumbalgia or common lumboradiculalgia, mechanical pain, inflammatory pain, fibromyalgic pain, neurological pain, chronic low back pain, postoperative chronic pain after valve replacement, osteoarthritis with chronic pain, one or more chronic nonmalignant pain disorders, Alzheimer’s disease and chronic pain, Parkinson’s disease with chronic Parkinson’s disease-related pain, and cancer with chronic pain.

The shortest study lasted four days [28], and the longest 18 months [29]. Eleven studies received approval from an ethics committee to conduct the study. Two studies did not provide this information [28, 30]. One study did not require ethics committee approval, as per French bioethics law, no approval was needed if the physical and psychological integrity of the patients was not compromised, chronic pain was recognized as an indication for MT, and verbal consent was obtained [31].

The intervention in most studies involved listening to music in a quiet room with a comfortable seating or lying area, without engaging in any other activities while listening. Other interventions included uninterrupted MT, as well as MT following the Heidelberg model [28]. Additionally, there was group               singing with a final concert [32]. Participants in two studies selected different types of music according to their current needs: cheerful and familiar music to relieve muscle tension, slow and melodic music for sleeping and relaxation, music to improve the mood during depression, and energetic music to boost energy during fatigue [33, 34].

Water and wave sounds were deliberately played in one study [35]. Another study selected only music that ranged between 8–150 Hz and 50–70 dB for the intervention group [17]. Simple, lively songs were sung after a vocal warm-up in one study [36]. In another study, only pieces by Mozart with a tempo of 60–80 bpm were played [37]. Two studies employed the U-Sequencing technique [29, 31].

The shortest intervention lasted 20 minutes, and the longest two hours. Some studies conducted one intervention per day, while others conducted two. In one study, only a single intervention was performed [38], and one study reported 12 interventions over three months [32]. The control groups were allowed to rest, read, or paint. The painting group held an exhibition at the end. Music was also provided for listening in two studies [33, 34], while in one study, music was combined with exercise [36] or tactile touch [27]. Ten studies mentioned that standard therapy was continued during the intervention. It can also be assumed for Siedlecki’s (2009) study, as it is an extended analysis of the 2006 study, in which standard therapy was integrated. Risk of bias studies included The risk of bias for each study is visually represented in Figure 2.

Allocation

Participants in the 14 studies were divided into two or three groups through a randomization process. Six studies were classified as having a low risk of bias because they used computer-generated methods [27, 33, 34, 39], block randomization with stratified envelopes [37], or a centrally organized list in advance [29] for group assignment.

Six studies provided no information on how the randomization was conducted and were, therefore, classified as having an unclear risk of bias [17, 28, 30, 32, 36, 38]. Two studies were classified as having a high risk of bias because the participants were alternately assigned to the intervention and control groups [35]. In the second study, participants admitted in even-numbered months were assigned to the intervention group, while those admitted in odd- numbered months were assigned to the control group [31]. Regarding allocation concealment, one study was classified as having a low risk of bias because an external member of the research team handled the communication of the randomization process [27]. Ten studies did not report specific details on allocation concealment [17, 28-30, 32-34, 36, 38, 39]. These were rated as having an unclear risk of bias. In one study, after giving consent, participants opened an envelope containing their group assignment (C for control group, E for intervention group). This study was rated as having an “unclear risk of bias” because it was unsure whether participants were aware of their group assignment [37]. Due to the alternating randomization process, two studies were also rated as having a high risk of bias for allocation concealment [31, 35].

Blinding

Eight studies did not provide information about blinding. One study reported that the participants were informed about the study, but it was later mentioned that the control group did not know the intervention group was receiving music, suggesting possible blinding, though this is not entirely clear [38]. In another study, participants knew whether they were in Group E or C after opening their envelopes, which allowed them to infer their group assignment [37]. These ten studies were, therefore, rated as having an “unclear risk of bias.” One study reported that randomization was done by an independent statistician, so that the participants and clinicians did not know to which group they were assigned [17]. Another study reported that the results were collected by an independent evaluator, but it was not stated whether the participants were blinded or not [31]. A further study reported blinding of the staff and the immediate removal of equipment after the intervention so that the assessor could not infer any information [29].

These three studies were rated as having a low risk of bias. One study was rated as having a high risk of bias because it was stated that participants knew in which group they were placed [32].

Regarding the blinding of outcome assessment, 11 studies were rated as having an unclear risk of bias because no information was provided. Three studies were rated as having a low risk of bias because they explicitly stated that the assessors were blinded [29, 31, 32].

Incomplete outcome data

One study reported five dropouts but still had enough participants to maintain statistical power [31]. Another study recorded four dropouts out of 64 participants, which was considered acceptable [34]. Seven studies showed no missing outcomes, resulting in nine studies being rated as having a “low risk of bias.” Three studies were rated as having a “high risk of bias.” One study initially reported 37 participants but later only 35, without mentioning the dropout rate [17]. The second study identified significant differences at baseline and included them as covariates in the analysis, but spontaneously formed a third group when some participants did not show up [36]. The third study recorded four dropouts and reported an initial, significant difference in the VAS measurement, which was not statistically verified later [33]. One study was rated as having an “unclear risk of bias” because it was based on an earlier study with 59 participants, but only 50 completed both the baseline and the 12-week assessment. The absence of nine participants was not explained [32]. Another study also received an “unclear risk of bias” rating because one outcome reported two p-values without explanation, which were not related to the outcomes of this review [27].

Selective Reporting

No selective reporting was found in 13 studies, which were rated as having a low risk of bias. One study mentioned conducting a follow-up, but some results were missing. Additionally, it did not specify how many men and women participated in the study, even though it was stated that there was no significant difference between them [36]. This study was rated as having a high risk of bias.

Other Bias

One study was rated as having a high risk of bias because there were three significant differences already present at baseline, and it was noted that these differences were not statistically controlled for in the subsequent analysis [33]. Another study had significant group differences at baseline, but this was addressed by using covariates in the main analysis [35]. This study and 12 others were rated as having a low risk of bias.

Effects of Intervention

Although each study examined different outcomes, this review focused solely on pain reduction. The measurement methods VAS, MPQ, and NRS have already been explained in the Introduction. This section directly addresses the results.

Pain

All studies assessed pain progression using various testing methods.

VAS

Six studies used the VAS [17, 28-31, 35]. All studies showed significant improvements in the intervention groups. Guétin et al. (2005) noted that the intervention group only showed significant improvements immediately after the session, and no significant difference was measured between the groups. Similarly, Nickel et al. (2005) found no significant differences in the current pain measurement between the groups, but there was a significant improvement in the last four days in the intervention group.

MPQ

Five studies used the MPQ, four of which used the short form [33, 34, 37, 38]. All studies showed significant differences between the groups. McCaffrey and Freeman (2003) found consistent significant differences, while Zimmerman et al. (1989) observed differences in all but one subcategory. Lin et al. (2020) observed significant differences only in the pain rating index emotional item. Siedliecki and Good (2006) examined two intervention groups and a control group. The combined music groups showed a significant pain reduction compared to the control group (p = 0.002), with other results reported as percentages. Siedlecki (2009), an extension of the 2006 study, investigated racial differences and found significant differences between races. Significant differences were observed between the intervention and control groups for Caucasians but not for African Americans.

Pain-O-Meter (POM)

The POM combines the VAS and the MPQ into a single tool for comprehensive pain assessment. The POM includes a 10 cm VAS to measure pain intensity and a list of sensory and affective words (POM-WDS) to evaluate the sensory and affective components of pain. The results can be aggregated into a  total score for pain intensity [40]. POMemo categorizes emotional pain terms on a scale ranging from worrying (=1) to terrifying (=5), whereas POMphys evaluates physical pain descriptions from soaring (=1) to tearing (=5) [27]. The POM was used to evaluate pain outcomes in the study by Skogar et al. (2013). No significant differences were measured between the groups. However, within the groups, the POM-VAS showed a significant reduction in pain intensity in both groups. Regarding the POM-emo and POM-phys, only the Tactile Touch group showed a significant improvement, while the Rest-To-Music group did not.

Pain Self-efficacy Questionnaire

The Pain Self-efficacy Questionnaire is a self-assessment tool consisting of ten items. Each item is rated on a 7-point Likert scale from 0 (“not at all confident”) to 6 (“completely confident”). Respondents indicate how confident they are in their ability to perform certain tasks despite their pain. The total score is calculated by summing the individual ratings and can reach a maximum of 60. Higher scores indicate greater confidence in the ability to achieve the desired outcomes despite pain [41]. The study by Kenny and Faunce (2004), which spontaneously formed a third group, showed no significant improvement between the singing group and the control group or between the singing group and the nonparticipating group. However, a significant time effect was observed for both the singing and control groups after six months. No information was provided on the comparison between the singing group and the nonparticipating group.

Pain-related Self Statements Scale

The Pain-related Self Statements Scale assesses situation-specific aspects of cognitive pain coping and includes the subscales “Catastrophizing” and “Coping.” These subscales are validated, sensitive to changes, and closely related to pain intensity and impairment due to pain experiences [42]. The study by Kenny and Faunce (2004) reported the following results for the Pain-related Self Statements Scale: There were no significant differences in active coping between the singing group and the control group, or between the singing group and the nonparticipating group. There was even a decrease in active coping in the singing group and an increase in the control group at the six-month follow-up. No significant results were found for catastrophizing either.

Oswestry Low Back Pain Disability Questionnaire

The Oswestry Low Back Pain Disability Questionnaire is a self-report instrument used to measure the quality of life and pain tolerance in cases of low back pain. It consists of ten sections, each with five statements representing increasing degrees of disability, along with a separate section for pain intensity. Each section can score a maximum of 5 points, leading to a total score of 50 points. This score is then converted into a percentage, with higher percentages indicating a greater disability [36]. The study by Kenny and Faunce (2004) again showed no significant improvement in pain disability between the singing group and the control group or between the singing group and the nonparticipating group. The singing group even showed an increase in pain disability, while the control group showed a decrease at the six-month follow-up. No information was provided on the comparison between the singing group and the nonparticipating group.

Roland-Morris Disability Questionnaire and 4-Point Scale The Roland-Morris Disability Questionnaire is a self-administered questionnaire consisting of 24 items that reflect daily activities. Each item is scored as 1 (applicable) or 0 (not applicable), resulting in a total score ranging from 0 (no disability) to 24 (severe disability) [43]. The study by Kullich et al. (2003) assessed the effects of MT on patients with chronic low back pain, including the use of the Roland-Morris Disability Questionnaire, and showed significant results in the     intervention group on days 10 and 21. However, the control group also showed a significant improvement on day 21. Additionally, Kullich et al. (2003) used the 4-point scale to measure spinal tenderness. The scale was divided into no, mild, moderate, and severe pain. The results showed a significant reduction in spinal tenderness in the MT group.

Pain Sensation Scale

One study used the Pain Sensation Scale by Geissner, which employs 24 adjectives to assess acute and chronic pain, based on the adjective list from the MPQ. Two models were developed: a 5-factor model with affective and sensory factors, and a 2-factor model that combines affective and sensory pain [44, 45]. The study by Nickel et al. (2005) did not find any significant differences between the groups using the Pain Sensation Scale.

NRS, Simple Visual Scale (SVS), Brief Pain Inventory (BPI)

The study by Rouch et al. (2018) used the NRS to examine the usual pain intensity over the past week (NRS-U) and the worst perceived pain over the last eight days (NRS-I). An SVS is used to assess the pain intensity. In the SVS, patients are asked to use a scale from 0 to 4, where 0 represents “no pain” and 4 represents “very severe pain” [32]. The study by Rouch et al. (2018) investigated the usual pain intensity (SVS-U) and the worst perceived pain of the last eight days (SVS-I). The BPI quickly and easily measures pain intensity and its impact on the lives of pain patients. Respondents rate their worst, least, average, and current pain intensity on a scale from 0 to 10, as well as the extent to which pain interferes with seven functional areas: general activity, mood, walking ability, normal work, relationships, sleep, and enjoyment of life [46] The study by Rouch et al. (2018) divided the BPI into BPI-I and BPI-R. The BPI-I measured pain intensity (sensory dimension, three items) and assessed the usual and worst pain over the last eight days. The BPI-R captured the interference caused by pain (reactive dimension, ten items) and examined its impact on daily life. The study by Rouch et al. (2018) did not focus on the pain measurement alone but combined it with the Big Five Inventory. As a result, the groups were combined regarding pain measurement, and the results were reported as percentages. Therefore, this review could not provide an answer regarding significant differences between the groups.

4. Discussion

14 studies were identified for this review. Almost all of them examined multiple outcomes, but this review focuses exclusively on the improvement of chronic pain. The use of various tests for measuring pain intensity is central in pain research. Notably, studies that employed the VAS and MPQ showed significant differences between the intervention and control groups, providing consistent results that highlight their clinical relevance. Additionally, the 4-Point Scale also delivered clear results [30].

Studies on pain assessment demonstrated that the VAS is considered a particularly reliable instrument, especially when compared to the NRS and VRS [47]. Another study also found a high correlation (r = 0.86) between the MPQ-SF and the VAS, further confirming the VAS as the preferred method for pain assessment [48]. Only the NRS was used in one study [32] in the those included besides the VAS and MPQ. Otherwise, eight other complex measurement instruments were employed. It is noteworthy that these studies produced less consistent results, raising questions about their precision and user-friendliness.

All participants were diagnosed with chronic pain, but some studies provided more detailed differentiation between various types of chronic pain. This led to differences in the comparability of the results, making it often possible to draw only general conclusions. This could be due to the fact that many of the studies were conducted before the precise classifications of ICD-11 were introduced when there was less emphasis on a clear definition of chronic pain. It would, therefore, be desirable to conduct further studies focused on specific diagnoses of chronic pain to enable more targeted comparisons.

The study by Kenny and Faunce (2004) reported significant differences between the groups from the outset. However, these were used as covariates in the main analysis. Notably, the study measured numerous outcomes, yet, no significant differences between the intervention and control groups were found, and, in some cases, results were not reported at all. Particularly peculiar is the fact that the singing group showed a deterioration in Active Coping and Pain Disability during the follow-up. This might be due to a change in the study design, where a third group was spontaneously introduced because some participants were missing. This adjustment raises questions about the statistical power and, consequently, the validity of the results, as the original design only included two groups, and ethical approval was granted on that basis. This could have compromised the overall validity of the study.

Further uncertainties arose in the study by Siedlecki (2009), which reported three significant differences at baseline that were not accounted for later. This may lead to biases in the results and could have been easily avoided if, similar to the study by Kenny and Faunce (2004), these data had been used as covariates. One study conducted only a single intervention [38]. It is questionable whether the results obtained are even comparable with other studies, or if it would have been better to treat it as a pilot study to explore whether a larger-scale study would be feasible.

The study by Skogar et al. (2013) was included despite methodological concerns, as the intervention and control groups were reversed. In this case, the intervention group received tactile touch therapy in addition to music, while the control group only listened to music. The inclusion of the study is justified because the control group essentially received the music intervention that was assigned to intervention groups in other studies. Notably, despite the lack of significant differences between the groups, pain relief still occurred, suggesting that the use of music alone can be very effective.

It was noticeable in the risk-of-bias assessment that an “unclear risk of bias” was frequently identified in the “allocation” and “blinding” categories. In fact, one study showed that results are deliberately not published. The reasons varied, ranging from uninteresting to unexpected results, but also the question of securing funding [49]. One possible reason for this could be that the participants were informed at the beginning of the study and presumably recognized themselves in the course of the study to which group they were assigned. The study staff may also have known whether they were working with participants from the experimental or control group. These circumstances may have led to a decision not to document these

aspects precisely, which explains the frequent lack of justification. However, blinding would be necessary to prevent performance bias and avoid any potential bias [50]. The studies demonstrated a variety of interventions used. Nevertheless, listening to music was a central aspect. Participants were allowed to choose from a pool of different music in some studies.

Research in psychology has shown that people prefer to make their own decisions rather than having decisions made for them. The freedom to choose enhances the sense of autonomy and promotes intrinsic motivation, leading to higher satisfaction and more positive emotions [51]. Positive affect, in turn, leads to pain reduction [52]. The ability to choose their own music might have been more enjoyable for the participants, leading to better emotions and, consequently, a reduction in pain.

Another study used group singing in a choir as an intervention [32]. Previous research has also found that group singing leads to positive emotions [53]. Three studies specifically used music and its properties for relaxation through the “U” sequence  (tempo, volume, frequency, orchestral size) and music by Mozart with a tempo between 60 and 80 beats per minute [29, 31, 37]. Relaxation helps to reduce chronic pain, as demonstrated by a systematic review in 2021 [54]. This may explain why significant differences were measured between the groups in these studies.

In summary, it can be concluded that music, whether individually selected, experienced collectively, or specifically used for relaxation, plays a valuable role in pain management. The promotion of positive affect through musical interventions is a key mechanism contributing to pain relief. The strengths of this review lie in the fact that many studies show significant differences in the use of music for treating chronic pain. Additionally, the frequent use of the VAS and MPQ allowed for a good comparability of results. Nevertheless, the review has limitations, including many “unclear risk of bias” ratings in blinding and allocation, heterogeneous pain diagnoses, and inconsistent study durations and interventions. Additionally, the varying formats of result reporting, such as p-values and percentages, made direct comparisons between studies challenging. One aspect to consider is that study selection and bias assessments were primarily conducted by a single author. However, uncertainties were resolved collaboratively within the group, and standardized assessment tools were applied to support consistency and reliability.

Recommendations for Future Research

Future studies should aim for larger sample sizes and longer study durations to increase the robustness and generalizability of the findings. Additionally, procedures for blinding and the allocation of participants should be explicitly documented to allow for a precise assessment of bias risk. A stronger focus should also be placed on standardizing intervention protocols to ensure consistency and comparability across studies. It would also be important for all studies to report results not only in percentages but also as p-values to clarify the effects.

An interesting avenue for future research could involve combining this approach with neuroscience, where the use of music in individuals with chronic pain is examined from the perspective of the neural mechanisms involved in pain relief, such as the activation of the prefrontal cortex or the modulation of stress and reward systems in the brain.

Acknowledgement

ChatGPT 4.0 was used in the preparation of this work for assistance with translation, text correction, and condensation. The authors subsequently reviewed and edited all content.

Conflict of Interest Statement

The authors declare no conflicts of interest.

Funding Sources

No funding or sponsorship was provided for this study.

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