Throughout the film, whenever a record player or radio is playing you note the music isn't the latest chart-topping pop. Part of that is down to the same wish to avoid anything that would set the film in a specific time frame, but it's hard to imagine he real-life equivalents of Thomas and his circle would have been grooving to the Top 40. For a start there wasn't a legal pop music radio station broadcasting on British soil at the time, and if there had been, it would have been seen as catering to the unwashed masses out there.
No, people in this little scene went about doing what they did, and doing it gave them enough to set themselves up in reasonable comfort and pursue other interests as they raised their heads above the parapet.
When Thomas finds himself in the RickyTick, with the Yardbirds in full flight it's instructive to note the studied almost-boredom that prevails throughout the audience. They only become animated when Jeff Beck smashes his guitar, and presumably, should something similar happen again it'd be a case of Yeah, seen that before [yawn].
The fact that Blow-Up contained footage of the Beck/Page era Yardbirds, a lineup whose sole recorded output was the single Happenings Ten Years Time Ago/ Psycho Daisies, was a large part of the reason I ended up in the theatre the first time, but its the accuracy and the look and feel that has brought me back repeatedly over the past forty-something years. While the plot line has its share of interest and intrigue it;s the chance to catch a glimpse of a short-lived scene that promised much more than it ultimately delivered that makes Blow-Up worth revisiting from time to time.