Recently I've noticed that most of the better singers in my choir are the ones who also happen to be pianists.
I think piano helps a little; certainly it should teach recognition of rhythm.In my experience it doesn't do much for the ability to sightsing intervals. The better singers in every choir I've ever been in have been those who play an instrument (other than piano), especially if it's one in the same clef they usually sing in. I have yet to meet a really confident sightsinger who does not have an instrumental background, though I'm sure there are some out there. I think there are two reasons for this. Most band instruments don't simply produce the right pitch without some player input - a trumpet player for example must buzz the right pitch with his lips, not just press the right key. Second, most instrumentalists play in ensembles where the beat keeps going with or without them, and they are forced to stay connected to time.
Recently I've noticed that most of the better singers in my choir are the ones who also happen to be pianists. Obviously having a musical background would help you a lot with singing and choral music, but it seems to be the pianists more than any other instrumentalists who really know what they're doing. Is there a reason for this?
And dont forget that people with an instrumental background have probably spent alot more time staring at notes than people without that background.
. Singing is the key to sight reading, play, rhythm and breathing.
Sightreading in particular is not very related to singing.