Tennant advises U2 on music.
The Pet Shop Boys singer said the band have discovered how difficult writing for the stage can be.
And the popstar claimed his own band are lucky that their music works so well for musicals, while it is much harder for U2.
He added: "I'm sure they're discovering that when you start to write musicals it's a lot more difficult than you might have thought, because your music has got to work theatrically.
"I think we're lucky that we can write music theatrically.
"It's very difficult for rock music.
"There's been a lot of debate over this, saying that rock music doesn't work because the rhythmic dynamic of it is not particularly flexible."