The Guardian, Paul McCartney describes how Harmonix first started pitching him on the product way back in 2007, using Metallica (presumably one of the band's songs running in an earlier Guitar Hero title) as an example of what could be done with The Beatles: Rock Band.
There were "a couple of grown-ups standing looking very foolish with these little plastic guitars playing to a screen", McCartney says. "And we're going, 'Yeah, all right... It just looks like a really bad band.' They said: 'We really can do a great one with the Beatles, and we'll show you.' So Ringo and I got a bit intrigued."
So, when McCartney says they looked like a really bad band ... is he talking about the people playing or the guys on the screen? Because, yes.