The MISSA BREVIS (ca.15') for SATB Double Choir and Soloists consists of just two works - a Kyrie and Gloria - which can also be performed independently:

1. KYRIE, Op.5 (ca.4'30) for a cappella SATB Double Choir, with SSA and SA Soloists:

SATB Choir 1: 2xS, 2xA, 2xT, 2xB (8) = min.2 voices per line for divisi (SSAATTBB)* (stage left side) + SATB Choir 2: 2xS, 2xA, 2xT, 2xB (8) = min.2 voices per line for divisi (SSAATTBB)* (stage right side) +

Gallery/Offstage Soloists 1: 2xS (for divisi) + 1xA (3) (SSA) (at a distance or offstage, and set antiphonally to:) Gallery/Offstage Soloists 2: 1xS + 1xA (2) (SA) (in a high and more distant gallery or offstage)

= 1. SSAATTBB + 2. SSAATTBB + 3. SSA + 4. SA; or minimum of 21 singers: 7 sopranos; 6 altos; 4 tenors, 4 basses

(* But ideally at least double these forces: 16 per choir, or 32 for the two choirs + 5 soloists = 37 singers)

SEE: https://britishmusiccollection.org.uk/score/kyrie-op5

AND ITS COMPANION PIECE:

2. GLORIA, Op.18 (ca.10') for a cappella SATB Double Choir, with 2 x SA Soloists. (There is the option to double the solo parts, if necessary.) The eight main vocal lines are sometimes further divided for fullness of texture and motivic completeness.

SATB Choir 1: 2xS, 2xA, 2xT, 2xB (8) = min.2 voices per line for divisi (SSAATTBB)* (stage left side) + SATB Choir 2: 2xS, 2xA, 2xT, 2xB (8) = min.2 voices per line for divisi (SSAATTBB)* (stage right side) +

Gallery/Distant Soloists 1: 1xS + 1xA (2) (SA) (at a distance or in a gallery, and set antiphonally to:) Gallery/Distant Soloists 2: 1xS + 1xA (2) (SA) (at a distance or in a gallery)

= 1. SSAATTBB + 2. SSAATTBB + 3. SA + 4. SA; or a minimum of 20 singers (24 if solo parts doubled): 6 (or 8) sopranos; 6 (or 8) altos; 4 tenors, 4 basses

(* But ideally at least double these forces: 16 per choir, or 32 for the two choirs + 4 soloists [the parts of which may be doubled to 8 singers] = 40 singers).

SEE: https://britishmusiccollection.org.uk/score/gloria-op18-et-arcadia-ego-a...

BOTH WORKS ARE BASED ON THE SAME CHORD SEQUENCE.