A big band instrument is a type of musical instrument that is typically used in a large ensemble, such as a jazz orchestra. The three instruments mentioned in the crossword solutions are the TUBA (4 letters), SAX (3 letters), and bassviol (8 letters). The TUBA is a large brass instrument that produces a deep, low-pitched sound. The saxophone is a woodwind instrument that produces a bright, mellow sound. The bassviol is a stringed instrument that produces a low, resonant sound. All three instruments are essential components of a big band ensemble.