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AcoustID fingerprints

AcoustID identifies recordings from the sound of your files. OpenTag computes a fingerprint locally, asks AcoustID for matches, then retrieves the chosen release's metadata and artwork from MusicBrainz.

Set up fingerprinting

  1. Use a desktop build on macOS, Windows or Linux. This source is not offered on Android or iOS.
  2. Install Chromaprint's fpcalc separately. OpenTag does not bundle it. Obtain it from the Chromaprint project or your package manager.
  3. If OpenTag cannot find it, enter the executable's full path in Options → Tag Sources → Online services → fpcalc program. Leave the setting empty for automatic discovery on the executable search path and common Unix installation locations.
  4. Open Tag Sources → API keys…. If this build has no AcoustID key, add your application's key using the registration address shown there.

Enter an executable path in fpcalc program, not a shell command or extra arguments. Files must be accessible and decodable by that fpcalc installation. A fingerprint process taking more than 2 minutes is stopped and reported.

Identify and review

  1. Select the album's files and choose Tag Sources → AcoustID (fingerprints)….
  2. Select Search. OpenTag fingerprints each file and ranks releases by the number of selected files matched, then match score.
  3. Select the correct release and choose Next. Compare the edition, track list, matches and artwork, then save.

Identified files are paired with their matched MusicBrainz recordings, including across discs. If files have overlapping candidate recordings, OpenTag reassigns compatible pairs when necessary to keep the greatest number of compatible fingerprint assignments. A direct free track keeps earlier assignments stable; this does not globally optimize match scores. Auto-match, Selection order and Suggest sorting arrange remaining files without replacing those fingerprint pairs. You can still move files manually; inspect the resulting assignments.

ACOUSTID_ID is offered per file only when that file was identified as the recording of its assigned track. Moving it onto another recording does not copy another file's AcoustID. If only ACOUSTID_ID is checked and no ID applies or cover is selected, the file is skipped.

Limits and privacy

A match identifies a recording, not necessarily your exact edition. Several releases can contain it, so the highest-ranked result still needs review. Files without a usable match do not gain an inferred AcoustID.

OpenTag sends fingerprints and durations, not audio files. It performs lookups only and does not submit new fingerprints. AcoustID requests are spaced about 350 milliseconds apart; MusicBrainz lookups use a separate spacing of about 1.1 seconds. Local fingerprinting adds to the time needed.