Via a Facebook post on Saturday, famed Canadian vocalist David Clayton-Thomas (of Blood, Sweat & Tears fame) announced that “I am officially retiring from the concert stage. I am now past my 80th birthday… having survived two heart surgeries and 60 years of rock & roll, it’s time to hang it up. If I can’t perform at the level people expect of me then I won’t perform at all… I won’t embarrass myself or disappoint my fans. My eternal gratitude to all the gifted musicians and hard-working crews who have travelled the world with me for six decades and made every night a magical experience… it’s been a trip. Our musical collaboration…