Do you mean copying your music files (mp3s, FLAC, etc) or do you actually mean your music library (i.e. MusicBee's files that govern how the music files are grouped and shown)?
If you mean your music files, your normal method of backing up files (Acronis or the like) should do. Copying your music folder also works provided all your files are housed there and not all over the place.
If you mean your library, you should back up the folder where your library file (musicbeelibrary.mbl) is stored. Some of it would be recreated from that file if lost, but if you have that whole folder you're sure to have what it would take to recreate your library in a usable state if an accident happens.
Personally, I have acronis backing everything on my system up to a dedicated drive and then I have carbonite backing the important stuff (including both things above) to the cloud.
I'm a big believer in the
3-2-1 backup rule.