By the time this vox ad had been printed the Beatles image was very different to the suits shown here - rather ironic considering the advert title...
Paul McCartney is playing his trademark Hofner bass guitar
Vox is the sound - the sound at the top. Like the Beatles, Paul Revere and the Raiders, the Rolling Stones. If you want to sound like the sound at the top, buy Vox. That's what's happening.
Paul McCartney and George Harrison playing live, in front of Vox amplifiers