FFT analysis catches the fake-320 MP3s and fake FLACs hiding in your library. Batch process thousands of files. No DJ software required.
The bitrate field in an audio file is whatever the encoder chose to claim. A track encoded at 128 kbps and then re-encoded to 320 still says "320 kbps" in the tag, but the audio has no information above ~16 kHz. That's the classic fake-320 — common in tracks from forum packs, P2P, free music sites, and a lot of the "320 mp3 packs" floating around. The same trick happens with FLAC: a lossy MP3 transcoded to FLAC looks like a high-resolution file but contains zero information the original MP3 didn't have. Spek can show you one file at a time. fakin'thefunk batch-processes but is Windows-only and paid. Neither lets you sort your whole library by score.
Supported today
Rekordbox · Serato DJ · VirtualDJ (incl. Favorite Folders) on Windows 10+ and macOS (Apple Silicon + Intel).
Real quality scoring requires reading the actual audio, not the tag. MLD's FFT pipeline analyses the spectrum frame by frame — where the energy drops off, whether high-frequency content matches the claimed bitrate, whether the encoder fingerprint matches the format claim. Fake-320 MP3s have a tell-tale cliff around 16 kHz that's invisible to bitrate-from-tag checkers. Fake FLACs (lossy MP3 transcoded to a lossless container) show the same cliff, just inside a wrapper that pretends to be lossless. MLD's scorer catches both, batch-processes thousands of files at once, and lets you sort your library by actual quality.
It's an MP3 file whose tag claims 320 kbps but whose audio was up-encoded from a lower-bitrate source (typically 128 or 192 kbps). The file is bigger than it needs to be, the tag says high quality, but the audio has the spectral footprint of the original lower-quality source. Common in tracks distributed through pack sites and forums.
Spek is excellent for inspecting one file at a time visually. MLD does the same FFT-based analysis but batch-processes your entire library, scores every file numerically, and lets you sort/filter to find the worst offenders. Think of it as Spek + a library-wide dashboard.
Yes. A FLAC made from a 128 kbps MP3 source has the same spectrum cliff as the original MP3. MLD's analysis runs on the decoded audio, so the wrapper format doesn't matter — the score reflects what's actually in the signal.
On a modern Mac or PC, MLD scores roughly 100–200 tracks per minute. A 10,000-track library finishes in roughly an hour. Results are cached, so subsequent scans are instant.
No. Folder Library mode is built for users without Rekordbox/Serato/VirtualDJ. Just point MLD at any music folder and quality scoring works the same as it does for DJs.
Smart Upgrade searches online sources for a cleaner version of the same recording and lets you preview, then swap. The original goes to the Trash (recoverable). It's a Pro feature, and you are responsible for ensuring you have rights to obtain the replacement content.
Free tier covers detection and viewing. Lifetime access is $49 — $19 for the first 100 DJs.
