Cathy's Army is a tender ballad featuring solo trombone. The other trombone parts are optional, making this a perfect chart for a band with incomplete instrumentation. In fact, the solo part can be played by an additional tenor or baritone saxophonist, making the piece suitable even for a band without trombones! No improvisation is required. The rhythm section parts are fully notated, and the written brass ranges are: trumpet G5, trombone F4.