suggestions for sounds for solo voices

see shoogles comment concerning advices to solo voices in the comment from Aug. 4th:

https://musescore.org/en/comment/760881

and the following discussion.

I don't get a satisfying idea for sounds in the mixer for solo singers. For bass I can imagine "trombone" but for other?
(btw. when I don't remember wrong there's no piece with solo voices an choir together in the b mass)

note (for orientation): look in "Ladaumtus te" for Soprano II, "Dominus deus" Soprano I and Tenore, "Qui sedes" Alto, "Quoniam tu solus" basso.