In its first two weeks, the Rock & Roll Hall of Fame app for iPhone and iPad has done something remarkable in an industry where most news about music buying is about how people don’t do it anymore: It convinced people to pay for music.

The $2 app includes information about 600 “songs that shaped rock ‘n’ roll,” and the company behind it reports an aggregate sales conversion rate of 31 percent. That means that in this two week period, every ten app purchases has already resulted in approximately three song purchases — an impressive ratio that the developer behind the app, Sideways, expects to rise.

“There was a 31 percent aggregate conversion rate within just the first two weeks,” said Sideways spokeswoman Liz Bazini. “While the number of app downloads will decrease over time, the in-app purchase rate will increase over time. Our conclusion is that iPhone/iPad apps with in-app music purchases work really well as a means of increasing music sales, which should be of significant interest to both artists and record labels.”

I’ll say.

Of course, plenty of apps these days, including popular interactive radio apps, include purchase links leading to song downloads on iTunes, and they don’t report this sort of success. Something must be different about this app, and so far as we can tell, it’s the level of curation and context surrounding each song.

These songs, sortable by decade from 1920 to 2006, were hand-picked for inclusion in the app based on their degree of influence over the rock n’ roll genre. Users can’t stream them in their entirety, but they can hear samples — and, perhaps more importantly, read original text about why each one was included.

It may not be enough to show people a list of music they might want to buy — they may need to know why they should buy them, and to be able to wander through the list learning more about whatever piques their interest, rather than listening to songs in sequence, the way we do with radio-style apps.

Perhaps there’s some truth to the argument that people still want to buy and own music; they might just might need more curation and context before they’re willing to commit. Proportionally speaking, it might be easier to sell music from a catalog of 600 than six million songs.