Mr Okun did work with many other vocal groups. I had the pleasure of meeting him once with Joe when he and I were looking at becoming a duo. Mr Okun (I feel funny calling him Milt, because he was Mr Okun to me--I always had the feeling my grandma would reach from the beyond and smack my head if I ever called someone twice my age by his/her first name, even if that person gave me permission) had an ear for what worked in harmonies and when the purpose of songs were best served by unison singing or just one voice alone. He was a brilliant musical director, BRILLIANT.