Reply To: Female singers and a male director
I’m a male chorus director as well, and I have had good results with vocal modeling using my falsetto register. I can’t sing the entire soprano range comfortably, so I will drop an octave when necessary. The female singers get good information on vowel purity, tone color, placement, etc… You might also ask a female singer to come to class one day and do a demonstration for your sopranos and altos. Someone from the local college would probably be willing to help. As an alternative, play a recording of a professional classical singer.
As far as the tone/placement issue is concerned, make sure they are keeping their tongues relaxed and forward, not drawn back in the mouth. What you want is a bright, clear vowel with a warm mellow tone (open, relaxed throat position). It is difficult for beginning singers to separate those two issues.