"[T]he CDDB database now includes nearly 3 million CDs and more than 36 million songs. Each day, users from ninety countries submit about ten thousand new albums to CDDB. In the US, Korea and Japan, Gracenote has editorial staff to “vet” the entries and “lock them down” to prevent modification by users. Because of the volume of entries, the editors are focused on the most popular content; of the most popular CDs, “the high 90% are locked down.”
For the smaller labels, Gracenote has a “content partner program” so that they can directly submit album and track metadata for their own CDs and lock them down.
Gracenote does not lock down the genre metadata, which is highly subjective. They allow for two different genres for each album, artist and song.
Gracenote licenses a CDDB Software Development Kit (SDK) to software developers. Most PC-based CD players and recorders use this kit, which is also available for Apple and Linux-based systems. Gracenote also provides an “Embedded CDDB” solution; for portable devices and others without an active Internet connection, this provides a copy of CDDB for storage on a hard drive."
Here’s another example where bottom-up contributions are mixed with a stricter controlled vocabulary.
07/07/04 update: Wired: The House That Music Fans Built.