SATB

In music, SATB is an initialism for soprano, alto, tenor, bass, defining the voices required by a chorus or choir to perform a particular musical work. Pieces written for SATB (the most common combination, and used by most hymn tunes) can be sung by choruses of mixed genders, by choirs of men and boys, or by four soloists.
There is a lack of general agreement on the initialisms and/or abbreviations for any but these, the four most frequently encountered voices.
Other initialisms/abbreviations often met with in this context include Tr for Treble, Mz (or similar) for Mezzo-soprano, Ba, Bar or Bari for Baritone and C for Contralto, this latter tending to define the gender of the alto(s) expected to sing the part which, if called A, might otherwise be thought suitable for Countertenors (Ct). SCTB is therefore commonly found in Romantic Italian opera choruses where the Alto singers portray a...