In his book, My Effin' Life, Geddy Lee indicates ABC's In Concert filming on October 11th, 1974, was followed by the filming of Don Kirschner's Rock Concert "the next night". However Ian Grandy confirmed via email that the two performances were separated by five days with Kirschner's filming taking place on October 16th. When asked what the band did during those 5 days, Ian responded "rehearsing at S.I.R. studios in L.A.".
"We ended our first stint with KISS in Texas and dashed across America to the suburbs of Chicago to open a show with Steppenwolf and Canned Heat, then flew to Los Angeles for Don Kirshner's Rock Concert and ABC's In Concert - our first national US television broadcast and also our first time flying first-class - hell, yeah. Mercury had ponied up for four seats, which meant one thing to us young sophisticates: free drinks all the way! We filmed In Concert at the Aquarius Theatre - pretty intimidating with the likes of Donovan and Sly and the Family Stone on the bill. When we arrived the next night for Don Kirshner's, George Harrison was backstage, but we were way too shy to go up and say hello to an actual Beatle. He was there to support his friend Billy Preston (whose manners, I can tell you, had not improved one iota since we last met: once again he pretended that he didn't know us)." - Geddy Lee, My Effin' Life