Musical Yokai

In Japanese folklore there is a belief that objects that are very old are able to gain a spirit and transform into a type of yokai known as tsukumogami. Sometimes this is because they have been used lovingly for a long time and are rewarded for their service. There are several musical instruments that are believed to transform into yokai if they are played for many years and then neglected by being stored away and not played any more. 
'The Biwa Player' - Tsukioka Yoshitoshi, 1874
Biwa Bokuboku
The most well-known is the biwa bokuboku which is often reported sitting alone in rooms playing sad music as a result of being abandoned by whoever used to play them so often. There are also tales of them dancing through empty homes making music as they go.
Toriyama Sekien in Gazu Hyakki Tsurezure Bukuro

Unknown artist

Koto Furunushi

If you ever hear music when no-one is around, it could be a koto furunushi. The koto is a Japanese stringed instrument which, if forgotten, can also transform into a yokai resembling a wild beast that can move on its own and play all the songs that had ever played on it.

Toriyama Sekien in Gazu Hyakki Tsurezure Bukuro
'Samurai and Koto Player' - Mizuno Toshikata, ca. 1910.