To find information about songs and music. There are many music database and identification services on the Internet that enable users to find missing track titles for their CDs and digital files, as well as identify songs by sound, singing or humming. There are also services that recommend songs to users based on their taste (see
music recommendation service). Following are the various ways music databases are searched.
Search by Disc Table of Contents
Although added later (see
CD Text), the only descriptive data (metadata) in the original CD music disc were a table of contents (TOC) containing track numbers and lengths. In order to display artist and song titles on the computer or add them to MP3 files when ripping CDs, several databases were developed that identify a disc by table of contents. See
music CD identification.
Search by Digital File Fingerprint
MP3, AAC and other compressed audio files contain fields (tags) for the names of the album, artist, tracks, genre, etc. Tags with missing or incorrect data can be updated with the correct data. An acoustic fingerprint of the file is computed and sent to a fingerprint database for matching. See
music file identification and
acoustic fingerprint.
Search by Audio Fingerprint
Songs can be identified by a sample of the actual sound being played on the radio. An acoustic fingerprint of the sample is computed and sent to a fingerprint database for matching. A fingerprint algorithm for audio is more sophisticated than one used for file recognition (above). The reason is that the audio sample can be a few seconds from any part of the song, whereas a digital file is entirely available for analysis. See
Shazam,
midomi,
Mobile MusicID,
MusicDNS and
acoustic fingerprint.
Search by Human Example (Sing, Hum, Tap, etc.)
People can find the name of a song or musical piece by singing or humming the tune or tapping out the melody and rhythm. See
midomi and
Musipedia.