Research if shakers and rattles should be different

It's not too clear what the difference is between https://musicbrainz.org/instrument/ac1e05c2-b4c2-4b0b-a5a8-87b902cefa06 and https://musicbrainz.org/instrument/0d2ef84f-197b-405b-9a7c-293bbe331e30 - it might be they're equivalent, and need merging, or it might be they're not, and need disambiguations and descriptions. 

Either way, "maracas" probably shouldn't be listed as a subtype of both.