It's Impossible

Jazz ensemble
Singer: Perry Como
Arranged David Tanner
vocal: Keys Eb

These are professional level big band charts arranged by Dave Tanner with individual parts written for:
brass (eg 4 trumpets, 3/4 trombones)
5 saxophones (eg 2 alto, 2 tenor, baritone)
4 rhythm (eg keyboards, guitar, bass, drums) and vocals