What is MusicDNS (now known as AmpliFIND)?
MusicDNS provides a simple, dependable, web service to identify digital music tracks and provide basic metadata. Using the approved open-source-licensed Open Fingerprint Architecture (libofa) SDK — or commercial licenses from MusicIP — any Internet-connected computer can query the MusicDNS web service. The Portable Unique IDentifier (PUID) that's returned will identify the master recording, regardless of digital format. The track metadata returned by MusicDNS can be used freely for any application needs.
m3lib Cache File Format