AcoustID is a project providing complete audio identification service, based entirely on open source software.
It consists of a client library for generating compact fingerprints from audio files, a large crowd-sourced database of audio fingerprints, many of which are linked to the MusicBrainz metadata database using their unique identifiers, and an web service that enables applications to quickly search in the fingerprint database.
If you have an unknown music file, one of the applications using AcoustID will very likely be able to tell you what song it is, who wrote it, and a lot more. In case AcoustID doesn't recognize the song yet, you can help by submitting it to the database, so that the next person trying to identify the same song will have more luck.
Learn more: https://acoustid.org/