Hello again, Choirman. Christmas must be coming up.
I'd beware of things like "decemviri" or "duoviri". They do occur in
classical Latin texts, put always referring to members of a board or
panel of judges.
"Triennium", "quadriennium" etc. also occur; three year period, four
year period.
But I can't find anything with specific reference to a group of musicians.
I'm going to go for the easy option.
Duo musici Ludoviciani
Tres ..........
Quattuor .......
etc.
Ed
P.S. A friend of mine is taking me on Saturday to a musical evening in
our parish church. She sings in the choir, and says they're singing
Latin on Saturday. I'm expecting Karl Orff's "Carmina Burana", but your
post reminds me that it could be other things.