Is your choir singing flat? Well, this may be a little controversial and many people will not agree with me, but there’s just one point I’d like to make here, and it comes from recent experience. This applies to less experienced choirs.
There’s no easy answer, and there is a great deal of good advice around (look down on the notes, always prepare your voice and have enough energy etc etc) so my suggestion can be ignored if you disagree with it.
What I suggest you do is simply sing loud.
Especially when you’re starting to learn a new piece.
I don’t mean that a pp piece should be sung ff. No, don’t try to blast everything, but give your voices a chance by opening your lungs and singing out.
Once the notes and texts are thoroughly known, then you can start to add the dynamics. By then the choir will know how much effort to put into each note or phrase, and that effort must be at least maintained when the volume is turned down.
What do I base this knowledge on? Well, teaching music and over 40 years of conducting male, mixed voice and children’s choirs has given me plenty of years to practice. However, I thought about this a lot more recently, since my move to France. I currently conduct a mixed voice choir of about 50 voices. It has a very wide range of experience and ability, but a substantial majority are absolute beginners.
We started about 4 years ago with rounds and very simple part songs (mostly SAB). There were only 20+ members then and we suffered from the usual problems, wrong notes, flat singing, everyone radiating towards the melody etc etc!
We’ve grown since then and now have easily enough men for separate tenor and bass sections. The wrong notes have all but disappeared (at least, as far as they ever will!) because there are now enough people in each section who know the parts and are able to lead the others down the straight and narrow.
But the flat singing can be a problem even with the most experienced choirs. I shall always remember a comment from a German friend of mine who conducted a choir from near Dortmund. He said to me after a joint concert in Yorkshire “Have you noticed how the piano always goes sharp between verses!”
I guess that’s the other way to explain it!