Apart from S.A.T

[sebstyoung]

is it possible to have a choir part that sings the 7th?

[JoanHall]

Not sure what you mean by "apart from SAT".  But if you have musicians playing along with a 3-part choir, the instruments will be playing the root of the chord themselves, so it's totally OK to leave out the root for the choir and have one of the parts sing the 7th instead.

Even with an a cappella song, you could probably still do it, but it might sound a little unusual (in my opinion the listener would probably still "feel" the root in the chord with their mental ear so it would still sound like a 7th chord, but if they didn't fill it in mentally then it would sound like a diminished chord).

And, of course, with a 4-part choir you can give the 7th to one of the parts and you still have a full chord.

[sebstyoung]

joanhall @ it again... thanks a lot. Really working on some personal gospel songs and I wanna do something off the usual. please share other helpful tips with little me.

[Docdb04]

It all dends on your voicing.  Even with S.A.T it can be done.  For example, if you are playing a C7 chord and you want the choir (section) to sing the 7th (B flat) note, you can voice it as T = B flat, A = C and S = E (You will not have a 5th in your voicing).  You can also do as JoanHall stated and voice T = B flat, A = E and S = G and have it rootless.  It all depends on the sound you are looking for as well as your chord structure.   

[choirlist]

Major 7 harmony can sound really cool. It will as Joan says sound unusual but if executed correctly can be impactful.

An example of maj 7th harmony being used vocally incase your wondering how it would sound is boyz 2 men silent night.

 

Boyz II Men - Silent Night acapella

heres the link . If your wondering where exactly in the song they go into maj7 harmony just let me know.