Best way to retrieve music metadata from audio files?
It appears music-metadata is the Node.js/desktop flavor of music-metadata-browser (intended for browsers).  The author doesn't explain the differences between the two, but maybe the desktop variant will be faster for you.

Synchronous anything is a mistake for an inherently parallel task like this.   Use fs.lstat instead of the fs.lstatSync.  If createLibraryEntry or dispatch touch the disk they should be replaced with async versions as well.

Worker threads are a thing but you probably don't need them, because disk access is what's slowing you down and async disk access doesn't require threads.  

If you have disk I/O that can't be asynchronized (if that's a word) by conventional callback functions, or if you've made everything async and it's still too slow, that is the time to consider using workers.