Only used when no Seed MIDI is given. Comma-separated instrument names -- the model writes a fresh piece for exactly this set. Leave blank to let the model pick its own instruments. Valid names: accordion, alto-saxophone, bag-pipe, bandoneon, banjo, baritone-saxophone, bass, bassoon, brasses, celesta, cello, church-organ, clarinet, clavinet, contrabass, dulcimer, electric-bass, electric-guitar, electric-piano, english-horn, flute, glockenspiel, harmonica, harp, harpsichord, horn, kalimba, koto, lead, marimba, melodic-tom, music-box, nylon-string-guitar, oboe, ocarina, orchestra-hit, organ, pad, pan-flute, piano, piccolo, recorder, shamisen, shehnai, sitar, slap-bass, soprano-saxophone, steel-string-guitar, strings, synth-bass, synth-brasses, synth-drums, synth-strings, tenor-saxophone, timpani, trombone, trumpet, tuba, tubular-bells, vibraphone, viola, violin, voices, xylophone.