FORTUNE — Just a decade ago, music streaming services like Spotify and Pandora seemed like a pipe dream: vast libraries of legal music that could be accessed with just a computer or phone. With Google entering the fray earlier this month with its Play Music All Access music service, streaming is definitely here to stay, and it’s one of many factors motivating artists and songwriters to mobilize and fight for a bigger piece of the pie.

One way in which songwriters are fighting for their work is by joining performing rights organizations, or PROs.The American Society of Composers, Authors and Publishers (ASCAP), which has been in operation since 1914, has seen a jump in membership in the past five years, gaining 300,000 members in the past four years alone. ASCAP has 460,000 members. Broadcast Music Inc. (BMI), another PRO, has 600,000 members, according to its website.

“We’re in a world where more music is being played more often on many devices,” says Paul Williams, ASCAP president and chairman of the board, as well the songwriter behind such hits as “Rainy Days and Mondays” and “The Rainbow Connection.” PROs are leading the fight in getting songwriters what they consider a fair share of royalties for any “performance” of a song, be it a play on a streaming service, radio, a video game, or television show, to name a few of the diverse avenues where music royalties can accrue.

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