This is one of the best all time. Back in 1986, The Manhattans, with Gerald Alston, did an acapella version on WBLS one night on Vaughn Harper. They did a great job, especially doing it "on the cuff".
I just listened to the version of this song where Gerald Austin sings lead. Gerald Austin is a gifted vocalist, no doubt at all about that, and Gerald sounds pretty on this song. However, Smitty, OMG--- Smitty pierces my very soul. Smitty goes beyond pretty into a whole other realm; he has that pleading, urgent, insistent tone convincing me that his love for this woman is a bottomless pit, and he cannot wait to be made as one with her; waiting another minute will cause him unspeakable pain, just as he does on “Can I” and all the songs he sings lead on. Smitty sounds as if he believes every word he’s singing so that he isn’t merely singing the notes but feeling the story as he delivers it. Smitty is unmatchable; he had his own very, special gift and he took it to the grave with him.