What Frank Sinatra was to the forties, what Elvis was to the fifties, what the Beatles were to the sixties, John Denver was to the seventies.

Ha!

Second the "Ha!" Maybe Elton John or Paul McCartney. If you're talking about cultural impact, perhaps Barry White.

I asked dh which musical act would he say defined the 70s, without the Sinatra/Elvis/Beatles set-up, and after saying something about how the 70s are by nature a little hard to pin down, he said Elton John, too.

I agree.

When I then read him DX's PBS quote, the laughter burst out of him along with a little spittle, so yeah, not John Denver (whose music I like).

There's no comparable figure in 70s pop music.

Elton was enormously popular with a peak in the early to mid seventies, but famously had hits every year for decades.

Bowie was probably the most influential figure in rock from the 70s, and would probably have the most five star albums during that decade. Also the greatest creative range with so many different musical phases.

The Bee Gees were enormous during the Disco era.

The biggest selling act of the 70s, who continues to still sell and were also enormously influential would be the Eagles. There influence, however, is bigger over country music than rock. Basically all country music started sounding like the Eagles after that period. But they never had the kind of Pop Moment Mania fandom the other artists did.

I agree.

The 70s are really hard to pin down, too. Pop had so many expressions at that time, from R&B to country to heavy metal, to the kind of rock and roll that currently seems to be on hiatus (but can sorta be found in country, and of course indy bands), to bubble gum pop, to crooners, disco, punk, etc.

When I then read him DX's PBS quote, the laughter burst out of him along with a little spittle

I am really thankful I wasn't drinking or eating anything when I heard it.

Pop had so many expressions at that time, from R&B to country to heavy metal, to the kind of rock and roll that currently seems to be on hiatus (but can sorta be found in country, and of course indy bands), to bubble gum pop, to crooners, disco, punk, etc.

Exactly so. The biggest shockwaves in pop during that era were entire new genres emerging and upending everything. That was as true of disco as it was of punk or metal.

Even the biggest game-changer of all, rap, is getting its start in the late 70s though it didn't break big until the 80s.

Fleetwood Mac probably comes the closest. They certainly hold their own compared to Sinatra, Elvis, and the Beatles in terms of behind the scenes drama.

That's a good one, Tom Scola. Yeah, Elton and Fleetwood Mac -- musically too.

Also? Sinatra by a huge margin sold way more records (and made better music) in the 1950s than he did in the 40s. His bobby-soxer moment in the 40s was a short-lived blip.