Clip from P.A. Pennebaker and Criterion Films DVD "The Complete Monterey Pop Festival"

Sunday, June 18, 1967 - The Monterey Pop Festival The WHO conclude their set with "My Generation" - Wally's 5 seconds on film and a great moment in rock history.

When the Who did their amazing set that night, nobody knew about the smoke bomb inside Keith Moon's drum set, especially Wally Heider, who up until that time had placed his normal set of condensers and dynamics on stage as was the norm. At the very end of the song, Wally steps into history as he avoids running into a dancing Roger Daltry and dodges guitar-shrapnel from Keith Townsend's antics as he rushes to save his microphones from certain destruction. I'm sure he nor anyone else had seen anything like this before. I don't think any condensers appeared on stage at the festival after that.

From the liner notes of the Criterion DVD set:

"After about four minutes of the song, Daltrey began to swing his handheld mike over his head; Townshend smashed his guitar strings against the mike stand before him, building up the feedback. Then he ran and played the guitar directly into his amp. The feedback went wild, and then he lit a smoke bomb before the amp so it looked like it had blown up, and smoke billowed on the stage. He lifted his guitar from his neck and smashed it on the stage, again, again, again, and it broke, one piece sailing into the crowd. Moon went psychopath at the drums, kicking them through with his feet, knocking them down, trampling on the mikes. The noise continued from the guitar as everything fell and crashed in the smoke."

Site Contributor Dale Manquen's account of the event:

"We were set up in a room to the left of the stage and down below. We had a spiral staircase for access to the stage level. A closed circuit TV feed gave us a shot of the stage so that we could see what was happening. I think we were running two machines, one of them a large black thing from Tom Hidley. Bill Halverson, one of Wally's guys, was also a 'full figured' person, but not quite as big as Wally.

We had been warned that The Who might damage some equipment. So there we were, watching the monitor and recording the audio when The Who went after one of the mics. I have never seen the movie of the Festival (where can I get a copy?), but my recollection is that they sheared off a mic cable with some hedge shears. Then they started slinging the mic around their heads and smashing it into the stage floor.

Well, this was more than Wally could stand! He and Bill Halverson both headed for the spiral staircase, but Bill got there first. What a sight to see! Both of these big men scrambling up the stairs, with Wally boosting Bill to make him move faster. Then all of a sudden Wally pops up on the TV monitor as he made is film debut as he tried to rescue his mic - probably a Shure 546!
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