Unstrumental is Calabasas High School's award winning contemporary mixed voice a cappella ensemble. The group is led by CHS Vocal Music Director, Michael Siegel, and Voice and Performance Coach, Alana Weiss, with coaching by singer/songwriter and CHS A Cappella alum, Mateo Gonzales.

Founded in 2001, Unstrumental is known for their powerhouse vocals, showstopping soloists, and dynamic stage performances. The group caters to CHS students who are passionate about performing and who may wish to pursue the performing arts in college or professionally. Unstrumental challenges its members to push themselves artistically and refine their skills through every captivating performance. The group boasts many alumni who have gone on to study music at prestigious universities and in some of the top a cappella groups in the country, as well as performers who have created successful contemporary music, stage, film and television careers.

Among the group's many accomplishments include being finalists at the 2025 International Championship of High School A Cappella (the competition made famous by the Pitch Perfect franchise), two-time featured performers at Carnegie Hall and four-time first place champions of the Los Angeles A Cappella Festival where they compete almost exclusively against collegiate groups . Unstrumental has received many awards for their outstanding staging, show-stopping soloists, and impressive vocal percussion. They are frequently featured on the national A Cappella anthology albums, Best of High School A Cappella and Voices Only and can be heard on Apple Music, Spotify, and all other major music platforms.