Four-part harmony using soprano, alto, tenor and bass is a common scoring in classical music,[1][2][3][4] including chorales and most Bach cantatas.
[5] The letters of the abbreviation are also used by publishers to describe different scorings for soloists and choirs other than four-part harmony.
[5]: 322 [7] A listing for Bach's Mass in B minor includes the maximum of SSATB soloists and SSAATTBB eight-part choir and also indicates that it contains choral movements for SATB, SSATB, SSATBB and SATB/SATB, as well as arias for individual soloists, and duets for SS, ST and SA.
Other letters of abbreviation, however with less consistency, have been used by publishers, such as "Tr" for treble (boy soprano), "Mz" for mezzo-soprano,[8] "Ba", "Bar" or "Bari" for baritone, "C" for both canto (the highest part) and contralto, and "Ct" for countertenor.
Similarly, when the tenor and bass are notated in one staff, the upper voice is marked by stems up, and both voices are written in bass clef, while the tenor is usually written in treble clef marked an octave down if it has its own staff.