{'fraction_non_alphanumeric': 0.02631578947368421, 'fraction_numerical': 0.004014272970561998, 'mean_word_length': 5.186206896551724, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Music's objective classification improves quality of music-induced analgesia studies.

We read with great interest the article entitled “Music-induced analgesia: How does music relieve pain?” by Lunde et al. We appreciate the thorough summary of the evidence supporting music-induced analgesia and the effort to address methodological difficulties accounting for its variability among published studies. The authors point this variability of findings as a result of factors “not attributable to music per se,” such as context and cognition. Although this may be partly the case, the authors fail to notice a fundamental concept: music should not be regarded as a single intervention but as a large group of heterogeneous interventions. The authors start by referring to the popular Rauscher et al. study of the effect of music on college students’ spatial– temporal performance. Although Rauscher et al. repeatedly used Mozart’s sonata K448 in different populations, the incorrect generalization of their findings led to the popular belief of the “Mozart effect” in both science and media, a perfect example of how sonata K448 was wrongly encompassed with the rest of Mozart’s compositions. Lunde et al. state that “contrary to theMozart effect, the terminology of music-induced analgesia does not posit one specific type of music.” When describing the type of music used in different studies, the authors use terms such as “classical music” or “spanish guitar,” probably because this is how the authors of the original works cited use these terms. Are “classical” music, “spanish guitar” music, or “Mozart” music similar? And more importantly, are they comparable as interventions? They are not. If Mozart’s “Requiem: K626” and “La Nozze de Figaro: K492” are compared, the reader may find the noticeable different sounds of each. Musicologists consider that terms such as genre or author are not accurate for music description. Music in research should be described as universally and objectively as possible: in music theory terms (ie, mode and tempo). To address the question of how music relieves pain, one must first ask what specific characteristics of music will be evaluated as an intervention. A more objective language when describing music will facilitate homogenization of clinical trials and reviews. As a recent umbrella review showed, music type and its characteristics are scantly described, which challenges the validity of music classification, and impairs comparison of therapeutic intervention across studies. In pharmacology research, a variation of the chemical structure of opioids may change its therapeutic effects completely. We seldom see the general opioid drug family being compared with placebo in clinical trials, that is because we understand the different pharmacologic profiles of morphine and any other opioid. When studying music, researchers assume “classical” music as the same intervention. Nonetheless, Mozart’s K626 starts in a minor mode, while K492 starts in a major mode, and their tempo are drastically different. Can this minor change produce a differential analgesic effect? The brain is activated differently by variable levels of consonance of music, while reductions in cortisol measurements vary according to music mode. A recent metaanalysis of Randomized Clinical Trials showed that music lacking lyrics had a more homogeneous analgesic effect. The music’s consonance, tempo, mode, and other inherent properties serve as a stable point of comparison, in contrast to the subject’s perception of music, which may vary based on knowledge, experience, and context. Furthermore, we can explore how music characteristics change its efficacy and use music as its own placebo. Then we may able to answer if music-induced analgesia is an effect of music per se, if it is an effect secondary to the emotions induced by music, or if it is simply an effect of cognitive distraction. In conclusion, we should see each musical piece as a specific drug, and treat it as such, then we may be able to overcome these obstacles. We invite the researchers in the field to avoid overlooking the inherent characteristics of music that also modify the analgesic response to it. One cannot suggest placebo control for future research without first understanding music’s classification. This common pitfall of music research is halting progress in the field and impeding homogeneity that will allow for comparison and academic collaborations in the future.