1) ABC and XYZ 2) Backup groups, often 3) Bands of three 4) Certain chamber groups 5) Chamber groups 6) Chamber pieces 7) Cream and Rush 8) Cream and The Police, for two 9) Dixie Chicks and the like 10) Fates and Graces 11) Fates et al 12) Gatlin Brothers et al 13) Gatlin brothers, and others 14) Graces and gorgons