Low bass singers doubling tuba parts?

[tubatooter1940]

I think it's a great idea.I used to play trumpet in a vocal triad and it
worked.Blending up was not as much a problem as we anticipated.Aug-
menting a bass section with voices will enrich both with some pleasant
textural surprises.
Tubatooter

[Shockwave]

If you can sing a tuba part in tune, every a cappella group within 200 miles will show up at your door with cash and a contract

[Steve Marcus]

I am also singing in a chorus that is preparing Rachmaninoff's "All-Night Vigil"

What a gorgeous piece to sing or listen to, especially in a highly reverberant space.