This consensus article, resulting from a roundtable discussion of experts in music-based rehabilitation, outlines central methodological challenges related to music-based neurological rehabilitation research. Issues related to treatment, outcomes, research designs and implementation are summarized, and a variety of solutions and future directions are proposed, including building collaboration and consensus on definitions and study designs, increased consideration of individual differences, and incorporation of technology. The article aims to improve the quality of music-based rehabilitation research to increase the chances of successful translation to clinical practice.

The authors discuss “The Framework for the development and evaluation of complex interventions,” but it is not immediately clear what this Framework is without going to the cited reference. As noted below, I would recommend a figure and/or a more explicit outline of the proposed Framework, so that it can be integrated clearly since it appears to be a cornerstone of the article. If the authors intend for the majority of the points in the paper to be viewed through the lens of the Framework, I also might consider moving the Framework section to the beginning. I have also highlighted a few opportunities (if space allows) for additional clarification and concrete examples to improve readability, particularly for readers who are less familiar with music interventions. One remaining point of consideration is whether we should consider within-subject crossover designs (vs. RCTs) given the heterogeneity of individual experiences with music and among clinical groups. Overall, this article features an important topic and represents a critical step toward building consensus within the field.

Introduction

• I appreciate the authors consideration of a breadth of neurological disorders (acquired brain injury, neurodegenerative diseases, and neurodevelopmental conditions), as many published papers focus on a single neurological condition. The authors may wish to feature this breadth throughout the paper by providing examples on how different interventions could be targeted/personalized according to the neurological population.
• I would recommend breaking up or streamlining the first sentence within the second paragraph to improve readability (the sentence that begins with “Recently, considerable interest has grown in music-based neurological rehabilitation…” (lines 79-82)
• In the second paragraph (lines 90-93), the authors might consider elaborating on the idea that musical activities can be adapted based on level of ability or stage of rehab. These activities can range from lower (listening) to higher (playing/reading) cognitive demands. They may also be applied independently or with caregiver assistance in the home during more chronic stages of rehab, lending increased accessibility/maintenance.
• The authors make a fantastic point about the need for collaboration and developing a consensus about the design and methodology of music-based studies (lines 100-102).

Treatment
- In lines 121-122, the authors note “Music-based interventions in neurological rehabilitation are complex interventions by nature because several interacting components need to be disentangled.” – clarifying or listing out these interacting components first would be helpful in interpreting the rest of this paragraph (also in line 135 which references the “multicomponent nature of music-based interventions”)
- Can the authors include a brief description of the “Template for intervention description and replication (TIDieR) checklist” for those who are unfamiliar?
- The authors make a great point about the benefits of describing in detail session materials and procedures. Another potential benefit to consider is that this will allow dissemination of research methods into clinical practice and foster sharing of resources
- Since music interventions may target emotional/mood/quality of life outcomes in addition to cognitive or motor abilities, consider adding these within line 131 after “cognitive or motor abilities”
- In line 131, should “exploitation” be replaced with “exploration”?
- The sentence found on lines 137-141 is a bit hard to follow; consider making the control group role within each population more explicit
- Consider moving “in active control groups” lines 145-147 to the next paragraph, so that the following paragraph focuses entirely on active control groups to improve flow.
- Instead of “their deficits and impairments” in lines 150-151, consider using more person-centered language such as “other areas of weakness”
- If space allows, consider including an example of a “usual and standard treatment” and the manner in which this may have synergistic effects (line 151)
- The authors make important methodological suggestions in lines 153 -161. If space allows, a brief example of an appropriate control group/intervention for a particular music intervention under investigation would be helpful.
- The authors note on line 164 that “a detailed reporting of all components of the control intervention is needed to identify the unique elements of the music-based intervention that promote the therapeutic effect”. Given how unique individual rehabilitation trajectories are, and how different one person's subjective experience/background in music can differ from another’s, wouldn’t it be equally important to include a detailed reporting of the individuals within the control group, as compared to the treatment group? Relatedly, because these uniquely beneficial elements may differ from person to person, it may be advantageous to consider within-subject crossover study designs (with vs. without the target intervention) that may have a higher likelihood of capturing a clinically meaningful effect (bearing in mind that we would have to thoughtfully account for recovery trajectories in more acute rehab contexts)
- As the authors note, music listening is a highly individualized experience. If space allows they may wish to elaborate the “tailoring” section beginning on line 169, especially in the context of within-subject designs where there may be more room for tailoring. This would align with the ultimate goal of determining whether an optimized/personalized music intervention is meaningfully improving outcomes for each individual. Other opportunities for tailoring might include adapting the intervention to be active vs. receptive depending on prior level of experience and remaining abilities, and adapting based on the person's goals at the outset (van der Steen et al., 2018; Hackett et al., 2022)
o van der Steen, J. T., Smaling, H. J., van der Wouden, J. C., Bruinsma, M. S., Scholten, R. J., & Vink, A. C. (2018). Music‐based therapeutic interventions for people with dementia. Cochrane Database of Systematic Reviews, 7.
o Hackett, K., Sabat, S. R., & Giovannetti, T. (2022). A person-centered framework for designing music-based therapeutic studies in dementia: current barriers and a path forward. Aging & Mental Health, 26(5), 940-949.
- Can the authors briefly elaborate on the tech approaches/techniques they mention in lines 188-189?
- When discussing the role of technology accessibility, the authors might include the need to obtain iterative user feedback from those using the tech – i.e., involving all potential user groups in the design and evaluation process (as outlined in Schultz et al., 2015 in the context of older adults; see also Nielsen, 1993 and Fisk et al., 2009)
o Schulz, R., Wahl, H.-W., Matthews, J. T., De Vito Dabbs, A., Beach, S. R., & Czaja, S. J. (2015). Advancing the aging and technology agenda in gerontology. The Gerontologist, 55(5),724–734. https://doi.org/10.1093/geront/gnu071
o Nielsen, J. (1994). Usability engineering. Morgan Kaufmann.
o Fisk, D., Charness, N., Czaja, S. J., Rogers, W. A., & Sharit, J. (2004). Designing for older adults. CRC press.

Outcomes
- When the authors note that researchers should “decide on generalizable outcome measures that are standardized and reliable” (line 243)– should these outcome measures also be clinically meaningful to participants and their caregivers?
- Fantastic points are made in lines 271-286 about considering baseline individual differences and variables/factors that may mediate the efficacy of the intervention (e.g., musical background) during analysis of the results.
- “Successful music-based interventions are founded on the assumption that skill transfer may occur from musical to extra-musical functions” (line 289-290) – is this true for all interventions? What about those that target mood/quality of life outcomes?

Research designs
- When the authors introduce “The Framework for the development and evaluation of complex interventions” (lines 329-330), it is a bit unclear what this framework is without referencing the citations. I might suggest either a figure or a more explicit outline or table to depict the Framework. Relatedly, the authors might consider moving the “Framework” section towards the beginning if the other components of the paper should be viewed through the lens of the Framework.
- Intervention groups could also be matched on other factors discussed above (past/current experience with music, neurological group, timecourse of recovery, etc.) (line 362)
- “baseline cognitive functioning” vs. “baseline impairment” to use more person-centered language (line 369)

Implementation
- “(i) mismatch of the generalization of research results to the target population” (line 382-383) – would a clearer way to say this be “failure to match specific interventions to target populations”
- Line 383 – I would suggest “integrating outcome measurement” to clarify that the issue relates to clinicians having the ability/familiarity with measuring/evaluating a given outcome
- Line 383 – I would suggest “lack of acceptance and familiarity with music-based interventions” to keep the language consistent

The authors have thoughtfully and graciously responded to all reviewer suggestions. I have just two minor requests for additional clarification:

• pg. 6 line 189-191 -- the second control intervention example is a bit unclear. I might suggest removing or replacing it with something more straightforward.

• pg. 8 lines 246-252 -- to provide more context to the new listed examples of tech-driven approaches, I would suggest including the target population that is featured in each cited reference. For example, "Participation of technology in music applications spans a variety of approaches, techniques, and clinical (or target) populations, including MIR for A population, enhanced feedback and sonification for B population, serious games in C populations and robotics and human-computer interaction within D populations." This will help the reader understand the elaboration in lines 249-252. Similarly, as written it is unclear what the context/intervention target is for the first example (MIR for music classification and instrument recognition?).