Insoul:
Do you mean singing them their note? If so just false sello (sp) or get one of the better sopranos to singing after you gave the note. You can also hit the note on the organ or piano.
Joy
You also could sing the part an octave lower in pitch and have the sopranos mimick you in their range. As a tenor/baritone, I did this often and when it didn't work then I'd use my falsetto or head voice.
Be Blessed, hope this helps
Jonathan