The Pet Shop Boys singer made the comment while talking about his group's ballet The Most Incredible Thing and their own 2001 stage musical Closer To Heaven.
Tennant said: "[In the '90s] there were lots of pop musicals, so it felt like a bit a cliché to work in that, though really most of those are just catalogue musicals.
"There's just Elton John, and Boy George, and Bono and The Edge, who are having a rather ghastly time in New York at the moment."
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."
Last week, Broadway actress T.V. Carpio was forced to take a two-week break from Spider-Man: Turn Off the Dark for mandatory bed rest after suffering an undisclosed injury.
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