Can Outtakes

My morning listening is laid out for me... I'm near completion of the first disc of an unoffcial 4CD Can Outtakes collection which surfaced around 2005 or thereabouts. I usually don't care for bootlegs but was listening to Mute's Can Live - 1971-1977 over the w/end and the time seemed right to delve in. There's been nothing terribly revelatory so far but interesting nonetheless - a version of Outside My Door lacks the energy and crunch of the Monster Movie cut, and there's a more rockabilly take of Man Named Joe. Wandering folk singer Tim Hardin is credited with an unlikely cameo appearance on one track (unceremoniously titled Rehearsal), although to my ears it sounds like him supplying the bluesy vocals on a second track as well (the Future Days flavored Soundcheck). At this point, Can were operating a revolving door policy when it came to vocalists so I can't say for certain. Anyone know for sure ? The best stuff are the band cutting loose on some trancey jams with Jaki Liebezeit in particular in hypnotic form. Onward to the Damo Suzuki era stuff !