Instrumental music is offered at Green Mountain through eight ensembles, including two concert bands, two string orchestras, a percussion ensemble, a jazz band, and the Green Mountain High School Marching Rams competitive marching band, which has represented the school at the Colorado Bandmasters Association state championships for more than twenty consecutive years. The concert bands often attend contests such as the Columbine High School Band Festival. The string orchestras are directed by instructor Carla Hawley and perform at concerts together, as well as in conjunction with the concert bands.