Here's a good discussion we had about it once before: http://tinyurl.com/tjmfj
My thoughts at that time:
"I've just given it a few listens, and if it was performed live exactly as it sounds, Fred didn't feature in this section, aside from the a couple of "Hey"s and one "bububbubdududb" sound.
There are only two 'vocal instruments' here, and due to the way the parts overlap and intertwine it's plainly evident that Brian is doing the trombone part (the main feature) and Rog is doing the muted trumpet part (a few bits here and there).
It IS just about possible that this was performed live, but I'm sceptical. Brian's part appears to be almost too good, and there's a couple of moments when he interjects the odd "hey" or "yeah" and they very nearly overlap his trombone part, as well as being at a completely different volume to the trombone part.
Oh yeah, and there's not a kazzoo in sight/earshot. Rog's part sounds absolutely nothing like one.
Conclusion: it's just about possible that what we hear was done live that way, but I suspect Brian re-did his trombone part and tidied it up a bit".
"Ok, I now officially retract my conclusion that Bri overdubbed his trombone part.
I've just listened to a couple of other bootleg versions of it and Bri performs the part to pretty much the same standard as on LK, and much the same things are going on.
Conclusion (revised edition): I need to give Bri more credit. It was played and sang live exactly as we hear it on LK".
"I just wanted to clarify that it was performed by Bri and Rog, that there were no kazzoos, and whether the Live Killers version was really performed live or not, as despite there being numerous bootlegs that prove that B & R did do this live, it was still possible that they'd 'cheated' for the LK release".
Gullibility and credulity are considered undesirable qualities in every department of human life -- except religion.