If you elect to use Menotti’s original 2-piano score (which is great, by the way!) Schirmer will also let you rent up to six books from the regular full chamber orchestration, and then you can simply “let go” of some of the 2-piano parts, and let those six instruments individual colors come thru. I once used the 2-piano version, and augmented it with the flute, oboe, clarinet, violin, cello and harp books, to make an 8-piece combo.