Interesting that you mention his voice. During a concert he was grabbed by a leg by a jealous fan making Frank fall to the pit resulting in a fractured leg and a broken rib, etc.. From then on, the pitch of his voice changed to what you are hearing today... Try now the live version of Muffin Man... it is spectacular... Good
He was pushed from behind, because the ‘security’ was out smoking weed during the encore ( this was in London, and the encore was “I want to hold your hand” by The Beatles. It’ out on CD/LP now). His voice dropped a major third, or something.
It stopped abruptly because at that moment it was about to segue into something else. It's a matter for eternal debate whether this song is just about trying to make organic dental floss or whether it's a metaphor for something else (either sexual or political). Anyway there was a lot of adlibbing in this rendition (e.g "yes indeed", "why don't you sharpen it then?" and "welll...." all of which were running jokes in the band at the time of the gig). Napoleon Murphy Brock was the other singer. A onetime musical-theatre performer, he's had a checkered career to put it mildly, but he was in George Duke's band for a few years in the late '70s. Ruth Underwood was the percussionist. If you're wondering what happened next - it's this ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-v6syzxyEzJU.html