The dominant source for free, legal, anytime, anywhere music. Scared yet, iTunes? Top 50 No. 15 
2. Apple Corps
The Beatles' label cracked open its Abbey Road vault to collaborate on The Beatles: Rock Band and a remastered catalog for a new generation of Fab Four fans. The group may have broken up 40 years ago, but it sold 3.28 million albums in 2009--without digital downloads.
3. Man Made Music
Whether he's recruiting John Legend to sing U2's "Pride" for the History Channel's MLK Jr. special, helping make Morgan Freeman the voice of CBS News, or sonically rebranding CNBC, Joel Beckerman says he's telling stories through sound--and growing his company  200%.
Backed by Universal, Sony, Abu Dhabi Media, and YouTube's infrastructure, Vevo is on its way  to becoming the Hulu of music videos.
5. Antares Audio Technologies
Invented in 1997 by a seismic data researcher for Exxon, Antares Audio's Auto-Tune was tweaked for pop--early on in Cher's "Believe" and later by robo-voiced hip-hop artists T-Pain and Kanye West. Despite a backlash led by Jay-Z, Auto-Tune has already defined an era of rap and R&B.
6. Third Man Records
White Stripes singer-guitarist Jack White's boutique label moved to Nashville in '09. Third Man makes handmade limited-edition 7-inch vinyl discs fast and cheap, and even released a mashup of Auto-Tune and Carl Sagan's Cosmos just after it debuted on YouTube.
7. Beats by Dr. Dre
The partnership between Monster, Interscope Geffen A&M Records chairman Jimmy Iovine, and Dr. Dre made giant studio-quality headphones  a fashion accessory. By late 2009, the black-and-red cans were at "Club Beats" pavilions at Best Buy.
The scrappy concert-ticket service uses software pioneered in the hedge-fund industry to let groups of friends buy tickets together with just a few clicks.
9. Insomniac Productions
Electric Daisy Carnival, its annual late-June, two-day electronica festival in L.A., grew to 135,000 attendees in 2009--as pricier festivals including Lollapalooza struggled.
While services such as Pandora pull song suggestions from proprietary catalogs, this little open-source app looks for tunes on the Web and on users' own hard drives and pulls them together into a single jukebox.