Since some years I am hacking on a music search library, which queries AcoustID (https://acoustid.org/), MusicBrainz (http://musicbrainz.org/) and freeDB (http://www.freedb.org/).
The idea is not only searching for a recording, but also getting the album / release information, and do some heuristics for matching the correct album for a directory of MP3 files.
“Since some years” means I started the project in my free time and later had some more important things to do.
If some admin of MusicBrainz lands on this page (since I coded the URL in the user-agent string):
I do not think that this project will generate much traffic in the future. If it will be finished someday, I will probably release it under an open source license.