freedb

freedb is a free CD and music data base service to look up textual metadata about music, audio or data CDs.

ACRCloud

Automatic Content Recognition (ACR) cloud services for Audio Recognition ( identify music, ads ), Broadcast Monitoring, Second Screen, Copyright Protection.

AudioTag

AudioTag.info — is a free music-recognition service.

LyricalPro

Learn the lyrics & become a Lyrical Pro

MelodyCatcher

Melody Catcher: The Internet Music Search Engine

WhoSampled

WhoSampled, the service that identifies music samples

beets

Beets is the media library management system for obsessive-compulsive music geeks.