Amazing Journey: The Story of The Who2007

Rob Ladd:
Typically, if the drummer were to add a second bass drum part, he would continue to lead on the downbeats with his right foot, and then any sort of extra notes would come out of the left. But that's not the way that Keith did it. When he would come to a section that required double bass playing, he would switch to a left-foot lead, which is the most insane thing I think I've ever heard of.