Trio Sonata is written for: Keyboard Solo (any type) 50482605 String Trio (Violin/Viola/Cello) 50482374 Double Reed Trio (Oboe/English Horn/Bassoon) 50482451 Clarinet Trio (Clarinet/Clarinet/Bass Clarinet) 50482450 Saxophone Trio (Soprano/Alto/Bari) 50482452. Mr. Harbison suggests performers try mixed configurations (ie: Violin/English Horn/Bass Clarinet).