Statement of problem: As players of single-reed wind instruments such as the clarinet and saxophone are likely to experience pain and trauma of the lower lip, a method to prevent these symptoms without disturbing the music quality and performance is required. Purpose: The purpose of this clinical study was to produce a custom music splint, an oral appliance for the players of single-reed wind instruments, by using sports mouthguard sheet materials and to determine its suppression effect on the pressure and pain of the lower lip and teeth and on fatigue and pain of the jaw. Material and methods: The soft type and soft and hard 2-layer type of sheet materials for sports mouthguards were used to fabricate the music splints. Each type of material has 1-mm and 2-mm thicknesses; therefore, 4 kinds of music splint were produced. The participants, students who played wind instruments in university orchestras, were instructed to use each music splint when playing the instruments for 1 week (for at least 3 hours for each music splint) and to answer a questionnaire about the effect of each appliance. Eighteen participants answered the questionnaire. Based on the usual usage of oral appliances when playing instruments, the participants were classified into 2 groups; oral appliance typically used (group OA) (n=7) and oral appliance not used (group noOA) (n=11). To determine the effects of the 4 types of music splint, a multilevel linear regression analysis was applied to evaluate the nested structure of the data (α=.05). Results: The use of the music splint significantly relieved pressure and pain on the lower lips. The soft type was more effective in group OA, and the thin type was more effective in group noOA. The thin- and soft-type music splints were associated with significantly better playing sensation and sound quality than other types of splint in both groups. Conclusions: The thin- and soft-type music splints can be effective and useful for suppressing oral symptoms when playing a single-reed wind instrument without disturbing the quality of the performance.