Pandora won an important appeals court victory on Wednesday, as the company defeated an attempt by songwriter group American Society of Composers Authors and Publishers (ASCAP) to increase the royalty rates the music-streaming service must pay.

ASCAP has been tussling with Pandora for years, but the case reached a resolution last year when a New York federal judge ruled that Pandora should pay 1.85 percent of its revenue to the songwriters' group. That's pretty close to the rate that Pandora had argued for, which was 1.7 percent—the same rate paid by terrestrial radio stations. ASCAP lawyers sought a tiered rate that would have reached 3 percent by 2015.

"[I]t was not clearly erroneous for the district court to conclude, given the evidence before it, that a rate of 1.85% was reasonable for the years in question," wrote the appeals judges.

In addition to validating (PDF) the lower court ruling, the appeals court also denied a request from Sony, EMI, and Universal to allow a "partial withdrawal" from ASCAP that would allow them to negotiate separate deals.

The victory is a needed, but small one for Pandora, which will continue to face long-term business concerns around copyright royalties. Financial statements show that Pandora pays about half of its revenue to copyright holders, the great majority of which goes to record companies. To license music copyrights, it's necessary to pay for both the copyright on the composition, often enforced by a group like ASCAP, and on the recording itself, which is usually owned by the record company.