If you are interested in any type of music, instrumental or vocal, it is important to exploit that interest to the fullest capability. You should participate in your school band or orchestra, and even look into starting your own music performance group with peers. If you are committed and able to, you should enroll in private lessons to expand your skills. You can show your concern for others by offering free lessons to local youth or holding a benefit concert for a local charity. It is important to provide a parameter for the admissions committee to judge you by, so compete in music competitions, and participate in various music festivals.
If you are confident that you are exceptionally skilled in your instrument, you should send a recording to the band or orchestra directors of the schools you apply to. This will allow them to evaluate the potential benefit of having you join their music group. Colleges love to accept a pool of applicants that will help them shine, so proving your musical worth is a great way of instilling confidence in your value as a member of the student body.