My wife is particularly keen on mechanical music museums (I like them too). Here are some we've been to:

• The Musical Museum at kew Bridge
• Keith Harding's World of Mechanical Music
• St Albans Organ Theatre
• Musée de Musique Mechanique (Dollon, France)

Also worth a mention is the Estonian Theatre and Music Museum, which I believe is the museum I visited around 2000 during some free time I had while visiting Tallinn on business. It may have changed since then but I was very warmly welcomed and given a personal tour (tags in Estonian were a bit of a challenge so it helped).

Simon