I think he likes the female vocals at the start of the song, that is the part he is walking off to while he’s shaking hands. It is uplifting and classical and pop rock at the same time. He’s off the stage by the time Mick starts singing.
I love the ending of that song... The Stones start riffing and cranking at the end...and you’d think the boys’ chorus would be awed by performing with the Rolling Stones....no...the the boys chorus meets them and matches them. The Stones up the heat but the boys match it and then soar above it. They own the Stones as they build to a fever pitch.
The Stones give up and play more sedately as the boys motor on.