AcoustID

AcoustID is a webservice for the identification of music recordings based on the Chromaprint acoustic fingerprint algorithm. It can identify entire songs but not short snippets.

By 2017, the free service had 34 million "fingerprints" in-store and every day acquired between 15 and 20 thousand new entries and answered around five million search queries. AcoustID is integrated into the audio file metadata editors Picard, Jaikoz and Puddletag, for example.

Chromaprint
In October 2009 MusicIP was acquired by AmpliFIND. Some time after the acquisition, the MusicDNS service began having intermittent problems. Since the future of the free identification service was uncertain, a replacement for it was sought. The Chromaprint acoustic fingerprinting algorithm, the basis for AcoustID identification service, was started in February 2010 by a long-time MusicBrainz contributor Lukáš Lalinský. The oldest entry in the DB is from 8 Oct 2010.

While AcoustID and Chromaprint are not officially MusicBrainz projects, they are closely tied with each other and both are open source. Chromaprint works by analyzing the first two minutes of a track, detecting the strength in each of 12 pitch classes, storing these 8 times per second. Additional post-processing is then applied to compress this fingerprint while retaining patterns. The AcoustID search server then searches from the database of fingerprints by similarity and returns the AcoustID identifier along with MusicBrainz recording identifiers if known.

Since 2013 Chromaprint is the only fingerprint supported by MusicBrainz.

Fingerprint ID
The fingerprint IDs are 8-digit and conform to /[1-9][0-9]{7}/. E.g.
 * https://acoustid.org/fingerprint/10374377 - one of the lowest numbers

AcoustID "track"
Groups of Chromaprints are given a UUID and can be reached via https://acoustid.org/track/, e.g. https://acoustid.org/track/a64cc174-c77c-47ee-ac1b-78015270dfe6.

The underlying chromaprints can be reached via fingerprint IDs, e.g. ID                                            Length  Sources https://acoustid.org/fingerprint/11799567	3:35	255 https://acoustid.org/fingerprint/41547743	3:36	152 https://acoustid.org/fingerprint/21463426	3:38	81

The linked MusicBrainz "recordings" can contain music of different performers, e.g.
 * This Goodbye Is Not Forever (original radio edit) // Touché // 3:38
 * This Is Not Goodbye // Melissa Etheridge // 3:35 // 1