Collins, Jimmy Carl Black, Pamela "Suzy Creamcheese" Zarubica, Frank Zappa, and Don Preston, London, circa 1968.
Collins was the primary voice of The Mothers Of Invention in their first incarnation, his creamy tenor croon nicely offseting Zappa's more nasal drawl and/or Roy Estrada's Pachuco interjections, falsetto or otherwise. He really did have the voice and the chops to be a great vocalist in the traditions/modes he genuinely loved—doo-wop and pop balladeering. But the zeitgeist had other plans for him. Enjoy him on Freak Out, Absolutely Free, and particularly Ruben And The Jets (the Zappa-label-issued Greasy Love Songs features that album's original, rather odder mix, and is highly recommended), and ponder how We're Only In It For The Money might have benefited from his more active participation therein.
Here is an intriguing profile of him from 2009 in a Claremont paper. Rest in peace.