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In many ways, I see the infrequency of recordings by rock groups as an anomaly of popular music. I tend to think that once these people become ultra-rich, they cease to be practicing musicians. Rather, many albums sound to me like they were made at least partly because two or three (or sometimes more) years had passed, and it was contractually mandated...

I'm sure that's a part of it, but not always the sole reason.

Yes. I suspect there's something cyclical outside of the contract. I just don't see many of these successful artists making an album spontaneously. Or maybe it's that it doesn't sound like it to me.

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One way to have a tremendous impact is to increase the frequency of this output.

A tremendous impact in/on what? Sales? Music history?

Both, I suppose. But mostly artistically.

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I can think of at least two bands which did this: The Beatles and The Police...both fired off a succession of albums with the frequency of one per year.

True. And both of those bands had an impact on the development of rock music due to their songs and their performing abilities. I'm sure there just as many (if not more) bands that have released albums yearly (or close to it) that haven't had a tremendous impact during their careers.

Yes, absolutely. Although I wonder if even these bands have a greater audience than they might have had they released less frequently.

I would argue two things. The first is that the yearly or near-yearly release schedule is often a product of early success. I can add Van Halen and Duran Duran to the list of bands that were on this kind of schedule during the first 5 or so years of their major label lives. So were U2, to a slightly lesser degree. Once they achieved a comfortable level of fame, they were able to take their time with further releases. Sting did this too. As did the Beatles in their solo years.

Very true.

The second is that some artists are simply more prolific than others. Elton John and Madonna are fairly consistent with their releases and have a large catalog because of it. Springsteen and Peter Gabriel are less so. But all four have played important roles in the development of the genre.

Yes, though at least in the case of Springsteen, he was incredibly prolific and active (especially in the studio) but only chose to release a few things sporadically.

I could even argue a third thing: quantity doesn't necessarily equal quality. But since the Police have already proved that, I don't have to.

I can't disagree with that, either. But an argument could be made that quantity equals some sort of frequency and therefore greater activity, which almost certainly has an impact on musicianship, compositional ability, and performance ability. I think that going off to save the rainforest or whatever is excellent. But it does mean that you have a year or two in which you're not really a musician, and that has at least some impact on your ability and career. Chris