Searching a music database for missing album information (metadata) in an MP3 or other digital audio file. Although MP3, AAC and other compressed audio formats include fields called "tags" for this metadata (see
ID3 tag), the data may be missing or incomplete. Such files can be identified by using an "audio tagger" program to analyze their waveforms and create an acoustic fingerprint that is matched against a fingerprint database. See
Gracenote MusicID,
MusicBrainz,
music CD identification and
music search.