The music identification company Gracenote has quietly become one of the most powerful companies in digital music and is building its reach in consumer electronics. The firm’s humble origins, however, began with the sweat of music fans worldwide.

But Gracenote’s transition from an open, public database to a profit-minded, private venture has irked some critics.

Gracenote is emerging as the information gatekeeper of the burgeoning digital media industry. AOL, Apple, Philips and Sony depend on the company to make their music players and gadgets easier to use.

New this year, Gracenote’s Mobile MusicID can identify snippets of songs through a cell phone.