glyr 1.0.10 Search engine for music related metadata
Glyr comes both in a command-line interface tool (
glyrc) and as a C library (libglyr).
The sort of metadata glyr is searching (and downloading) is usually the data you see in your musicplayer. And indeed, originally it was written to serve as internally library for a musicplayer, but has been extended to work as a standalone program which is able to download cover art, lyrics, photos, biographies, reviews and more.