For the remaining songs in Famous Music’s catalog — and the vast majority of the music publishing industry’s collective catalog — there is insufficient demand to justify the costs of publishing tablature.

Image Credit... Andy Manis for The New York Times

As a result, guitarists who want to know how to play less mainstream songs have gone to sites where amateurs post tablature. Under this agreement, MusicNotes, publishers and artists will essentially earn money from an army of volunteers, who are creating content that the publishers are not creating on their own.

Tim Reiland, chairman and chief financial officer of MusicNotes, which is based in Madison, Wis., said publishers would receive “a very healthy split” of the advertising dollars.

“We’ve got lots of work here to get the publishers signed up, but we think they should,” Mr. Reiland said. “We think it’s a good deal.”

MusicNotes bought MxTabs.net, one of the most popular guitar tablature sites, last year as it came under legal attack by music publishers. Publishers claimed that even incorrect versions of music notation violate copyright laws, since the postings represent “derivative works” related to the original compositions, to use the legal parlance.

The guitar tablature sites were typically small operations, running on little more than revenue gleaned from Google text ads. Many shut down rather than challenge the publishers in court. (Ultimate-Guitar.com, which has a New Jersey phone number but claims that it is based in Russia and that it complies with Russian copyright laws, still operates. Its advertisers include AOL, T-Mobile and Dell, among others.)