It was the highlight of my brief stay in Bologna. There IS an audio-guide in English, and I recommend purchasing it. The museum has lots of relics, period instruments, scores, and material pertaining to the early Renaissance and Baroque. Also, pretty informative about music in Bologna over the centuries as well. See also the page from an autograph Mozart score. I stayed well over an hour.
If you own or manage Museo Internazionale e Biblioteca della Musica, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.