To the Editor With great interest, we have read the recent article “Novel web-based music re-engineering software for enhancement of music enjoyment among cochlear implantees” by Hwa et al. (Otol Neurotol 2021;42(9), 1347–1354), which reports on a music preprocessing method for cochlear implants (CIs) and presents an evaluation with CI users. Although we acknowledge the novel contributions of this study, we disagree with claims made by the authors regarding the novelty of “music re-engineering for CIs” per se and the first use of harmonic/percussive source separation (HPSS) methods in this field, and like to point toward a number of relevant publications from our groups, which have not been considered in the mentioned article. In fact, music preprocessing for CIs has been investigated for almost a decade now. In their pioneering work, Buyens et al. (1) studied the effect of music remixing on music preferences in CI users and found that remixes with amplified vocals, bass, and drums were favored over the original mix. This finding led to the development of several music preprocessing algorithms. HPSS (e.g., Ono et al. (2), Driedger et al. (3)), and remixing was first proposed in the context of music processing for CIs by Buyens et al. (4–6). As an alternative to the HPSS approach, deep-learning–based algorithms for blind source separation and remixing were also derived and evaluated (Pons et al. (7), Gajȩcki and Nogueira (8), Tahmasebi et al. (9)). A different strategy based on dimensionality reduction and sparse subspace tracking methods in the time-frequency domain, which is particularly suited for classical music, was proposed by Nagathil et al. (10,11) and Gauer et al. (12–14). Lentz et al. (15) combined the dimensionality reduction approach with HPSS, facilitating its application to a wider range of music genres. An overview on many of these approaches was presented by Nogueira et al. (16). It seems that both authors and reviewers of the article mentioned previously have completely overlooked all of these publications. We hope that, with this letter, we may contribute to bridging apparently disparate scientific communities. Rainer Martin, Ph.D. Institute of Communication Acoustics Ruhr-Universität Bochum Germany [email protected]Wim Buyens, Ph.D. SoundTalks, Leuven, BelgiumAnil Nagathil, Ph.D. Institute of Communication Acoustics Ruhr-Universität Bochum GermanyWaldo Nogueira, Ph.D. Hanover Medical School and Cluster of Excellence “Hearing4all,” Hanover GermanyBas van Dijk, Ph.D. Cochlear Technology Centre Cochlear Ltd., Mechelen, BelgiumJan Wouters, Ph.D. Department Neurosciences KU Leuven, Belgium

Background: Although for most cochlear implant (CI) users good speech understanding is reached (at least in quiet environments), the perception and the appraisal of music are generally unsatisfactory. Purpose: The improvement in music appraisal was evaluated in CI participants by using a stereo music preprocessing scheme implemented on a take-home device, in a comfortable listening environment. The preprocessing allowed adjusting the balance among vocals/bass/drums and other instruments, and was evaluated for different genres of music. The correlation between the preferred settings and the participants' speech and pitch detection performance was investigated. Research Design: During the initial visit preceding the take-home test, the participants' speech-in-noise perception and pitch detection performance were measured, and a questionnaire about their music involvement was completed. The take-home device was provided, including the stereo music preprocessing scheme and seven playlists with six songs each. The participants were asked to adjust the balance by means of a turning wheel to make the music sound most enjoyable, and to repeat this three times for all songs. Study Sample: Twelve postlingually deafened CI users participated in the study. Data Collection and Analysis: The data were collected by means of a take-home device, which preserved all the preferred settings for the different songs. Statistical analysis was done with a Friedman test (with post hoc Wilcoxon signed-rank test) to check the effect of "Genre.'' The correlations were investigated with Pearson's and Spearman's correlation coefficients. Results: All participants preferred a balance significantly different from the original balance. Differences across participants were observed which could not be explained by perceptual abilities. An effect of "Genre'' was found, showing significantly smaller preferred deviation from the original balance for Golden Oldies compared to the other genres. Conclusions: The stereo music preprocessing scheme showed an improvement in music appraisal with complex music and hence might be a good tool for music listening, training, or rehabilitation for CI users.

Music appreciation remains challenging for cochlear implant users. In previous studies a strong negative correlation was found with cochlear implant subjects between music appreciation and music complexity. In this paper, music features that contribute to music complexity are investigated and related to a music preprocessing scheme for cochlear implants, in which a complexity reduction is achieved in an attempt to increase music appreciation. First, a complexity rating experiment is performed with pop/rock music excerpts and a linear regression model is developed to describe this (subjective) music complexity based on different music features. Subsequently, this model is used to validate the complexity reduction in the music preprocessing scheme and to provide an indication for the preferred setting for the balance between vocals/bass/drums and the other instruments for cochlear implant subjects.

Objective: Listening to music is still one of the more challenging aspects of using a cochlear implant (CI) for most users. Simple musical structures, a clear rhythm/beat, and lyrics that are easy to follow are among the top factors contributing to music appreciation for CI users. Modifying the audio mix of complex music potentially improves music enjoyment in CI users. Methods: A stereo music preprocessing scheme is described in which vocals, drums, and bass are emphasized based on the representation of the harmonic and the percussive components in the input spectrogram, combined with the spatial allocation of instruments in typical stereo recordings. The scheme is assessed with postlingually deafened CI subjects (N = 7) using pop/rock music excerpts with different complexity levels. Results: The scheme is capable of modifying relative instrument level settings, with the aim of improving music appreciation in CI users, and allows individual preference adjustments. The assessment with CI subjects confirms the preference for more emphasis on vocals, drums, and bass as offered by the preprocessing scheme, especially for songs with higher complexity. Conclusion: The stereo music preprocessing scheme has the potential to improve music enjoyment in CI users by modifying the audio mix in widespread (stereo) music recordings. Significance: Since music enjoyment in CI users is generally poor, this scheme can assist the music listening experience of CI users as a training or rehabilitation tool.

OBJECTIVE:Music perception and appraisal are generally poor in cochlear implant recipients. Simple musical structures, lyrics that are easy to follow, and clear rhythm/beat have been reported among the top factors to enhance music enjoyment. The present study investigated the preference for modified relative instrument levels in music with normal-hearing and cochlear implant subjects.DESIGN:In experiment 1, test subjects were given a mixing console and multi-track recordings to determine their most enjoyable audio mix. In experiment 2, a preference rating experiment based on the preferred relative level settings in experiment 1 was performed.STUDY SAMPLE:Experiment 1 was performed with four postlingually deafened cochlear implant subjects, experiment 2 with ten normal-hearing and ten cochlear implant subjects.RESULTS:A significant difference in preference rating was found between normal-hearing and cochlear implant subjects. The latter preferred an audio mix with larger vocals-to-instruments ratio. In addition, given an audio mix with clear vocals and attenuated instruments, cochlear implant subjects preferred the bass/drum track to be louder than the other instrument tracks.CONCLUSIONS:The original audio mix in real-world music might not be suitable for cochlear implant recipients. Modifying the relative instrument level settings potentially improves music enjoyment.

Music perception and appreciation remain generally poor in cochlear implant (CI) users. Simple musical structures, a clear rhythm/beat and lyrics that are easy to follow are among the top factors to enhance music appreciation. A music pre-processing scheme for CI users is described in which vocals and percussion are elucidated using harmonic/percussive sound separation. The scheme is capable of modifying relative instrument level settings for improving music appreciation in CI users. The scheme is assessed with normal hearing subjects (N=5) using a pairwise comparison analysis and CI simulated music excerpts. All test subjects except one significantly preferred the music excerpts from the music pre-processing scheme.