A musical composition for four instruments (usually in the form of a sonata with four movements) or a performance involving four instrumentalists, each playing a different part.

instrumental duet; a musical performance where two instruments play different parts together

A musical composition for three instruments; also refers to the group of three musicians performing such a piece.

An octet; a musical ensemble consisting of eight performers or a musical composition for eight instruments or more voices or instruments.

a musical composition for six instruments or voices; a group of six performers