How-to

How to find duplicate songs across different formats

Acoustic fingerprint matching catches the same recording even when the filename, tag, format, or bitrate disagree. Mac & Windows, no DJ software required.

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The problem

You probably have several copies of the same song scattered across formats: a 320 kbps MP3 from one purchase, a FLAC from a CD rip, an iTunes Plus M4A from an old library, maybe a 192 kbps version still hanging around from a decade ago. Filename-based tools (dupeGuru, Gemini) see four different files. Tag-based tools (most music-app dedupe) see four different files. None of them match the same recording across formats — because the fingerprint they use isn't acoustic.

How Music Library Doctor does it

1 Install Music Library Doctor (macOS 11+ or Windows 10/11). Folder Library mode is the right pick if you don't use DJ software.
2 Add every folder that might contain duplicate copies — Music, iTunes Media, Downloads, external drives.
3 Run Duplicate Scan and enable Acoustic mode. MLD computes a Chromaprint fingerprint for each file (the same algorithm MusicBrainz Picard uses).
4 Review groups. The Group Scorer recommends the best copy to keep based on bitrate, file size, format, and folder location. A FLAC will typically rank above a 320 kbps MP3 of the same recording.
5 Move losing copies to Trash (reversible until you empty it). Nothing is hard-deleted; the kept copy stays in place.

Supported today

Rekordbox · Serato DJ · VirtualDJ (incl. Favorite Folders) on Windows 10+ and macOS (Apple Silicon + Intel).

Why native integration matters

Acoustic fingerprinting reads the audio waveform itself and produces a compact hash that's stable across formats — a 320 kbps MP3, a 192 kbps re-encode, and a FLAC of the same recording all produce nearly identical fingerprints, even with different tags or filenames. MLD layers a quality-aware scorer on top: the Group Scorer ranks copies by bitrate, file size, format, and folder location, so you can auto-accept the best copy per group without inspecting every one.

Frequently asked questions

What is an acoustic fingerprint?

A content-based hash derived from the actual audio signal. Two files with different tags, bitrates, or filenames match if they contain the same audio. Chromaprint is the open-source algorithm MLD uses — also used by MusicBrainz Picard.

How long does an acoustic scan take?

First pass on a 10,000-track library: 10–30 minutes (audio decoding is the bottleneck). Results are cached, so subsequent scans are instant.

Will it match a remix and the original as duplicates?

No. The fingerprint reflects the actual audio. Different mixes, different masters, and remixes generate different fingerprints — only acoustic-twin copies match.

Does it work on external drives or NAS?

Yes. Any folder path works, including USB drives and SMB/AFP/NFS mounts. Scan speed depends on disk speed, but functionality is identical.

Is anything uploaded?

No. Fingerprints are computed locally and stay on your machine. Audio files never leave the computer.