Thanks, Jeri: We actually do a variation of sorts on marching in place. I kinda do a dip with my guitar when it's time for the person who has trouble catching the beat is singing lead. Most of the time it works. Unless he's looking the other way. Like most problems, there are ways to compensate. We did have a wonderful singer in our group who had sung solo all of his life in a black church. In black churches, the soloist gets up and starts singing, and the piano or organ player has to poke around and figure out what key he is in. Because of that, soloist don't have to "hear" keys. When this person was singing with us, I'd play the WHOLE melody on guitar as an introduction, he'd smile at me that he had it, and then launch off in a completely different key while we were singing harmony in the key I was playing in. Then it was a matter of musical chicken to see who give in first. I learned to stop playing guitar, and we'd have to shift into the lead's key and adjust our harmonies. I've heard black gospel quartets go completely through a song with the band and harmony singers singing in different keys. Having trouble transcribing rhythms onto paper sounds highly preferable to me.
Jerry