Unstrumental is Calabasas High School's award winning , competitive contemporary 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. Committed to artistic growth, Unstrumental challenges its singers to push their limits and refine their skills through every captivating performance. This competitive group caters to CHS students who are passionate and serious about performing and/or who wish to pursue the performing arts in college or professionally.

Among the group's accomplishments include being finalists at the 2025 International Championship of High School A Cappella, two-time featured performers at Carnegie Hall and three-time first place champions of the Los Angeles A Cappella Festival, where they have competed almost exclusively against collegiate groups and received numerous awards for their outstanding staging and show-stopping soloists. Unstrumental boasts many alumni who have gone on to study and perform music at prestigious universities and in some of the top a cappella groups in the country, as well as singers who have created successful contemporary music, stage, film and television careers.