"...Wiktor's a Jekyll-Hyde personality..." - Lycos Music
Usually it's placed just above the string parts using 2 staves. One for SA and the other for TB.
As to 2 staves vs. 4 for the SATB: it would probably depend on how active/independent the voice parts are. Relative "chorale" style could certainly use 2 staves. It's not surprising that the Brahms you mentioned uses 4.
Just my 2 cents.
I don't have a single orchestral/choral score that has the voices on 2 staves.
But if your music is not complex, then there's no reason not to save a bit of real-estate.
^ I agree, if it's something simplistic, like a choral, the choir will (should be... never know with singers ) able to follow their parts quite easily.
It's been 40 years since I've been in a choral group, but I don't recall ever having just 2 staves - it was always 4 (or 8 for double chorus). That is certainly the case in the scores I still have. The only exception I found to "one staff per voice" was Kodaly's Missa Brevis that had occasional divided parts, but not a double chorus. The divided parts shared a staff. (I assume those were supposed to be divided parts. We were just a college choir. Maybe professionals sing double stops. )
If you just have 2 staves for 4 voices, where do you put the baritone voices?
In 4 part groups the baritones and bases get lumped together, I think. And if the bass line gets divided, the baritones take the higher line. Although the bottom line is labeled "Bass" I think it's usually more of a baritone line. (I could be wrong.)
having sung in a professional opera chorus, I can tell you that choral parts vary enormously.
they are generally notated on four staves, one per part (S.A.T.B).
However, when there are divisi sections, then parts can be on as many staves as are required.
Some opera choruses I've seen had three or more women's parts divided on as many staves as needed, with the men divided on three staves with tenors baritones and basses.
One of my own choral works for mixed voices, a capella, has sections in 2-3 staves, and others on as many as 12.
there's no real standard as far as notation of a choral part is concerned. it's as many staves as are needed for the notation to be clear.