Fast and Furious Fourier Transform
A while ago, MusicBrainz used a technique called TRM for associating audio fingerprints with tracks. This relied on a proprietary, non-free database controlled by a for-profit company.
Your choices were to either use it and have music fingerprinting, or to not have the ability to fingerprint, since no one who knew how to develop a free database was doing so.
After some time with TRMs, MusicBrainz underwent a transition to PUIDs, and after running in parallel for some time, TRMs were dropped. PUIDs rely on a proprietary, non-free database controlled by a for-profit company.
Amazingly, things have changed. Now you can use free software to contribute to a publicly-available database.
If you have a music collection cleanly and properly tagged with MusicBrainz IDs, I urge you to participate in this project.