A music box or musical box is an automatic musical instrument that produces sounds by the use of a set of pins placed on a revolving cylinder or disc so as to pluck the tuned teeth of a steel comb. They were developed from musical snuff boxes of the 18th century. Some of the more complex boxes also have a tiny drum and bells, in addition to the metal comb.
More useless info: the band Wintergatan's marble machine is also a music box. This cache is a little bit less complex
This forms part of the Puzzle Containers Series, the others can be found here:
Puzzle Containers 1 - Bottlelock = GC67T4P
Puzzle Containers 2 - The Ultimate Renaissance Man = GC67WVH
Puzzle Containers 3 - Spin the Box = GC67KXR
Puzzle Containers 4 - Electricity Rebooted = GC6A98V
Puzzle Containers 5 - String Theory = GC69D1W
Puzzle Containers 6 - Nursery Rhymes = GC69XG7
Puzzle Containers 7 - Big In Japan? = GC6BPKQ
Puzzle Containers 8 - Balancing Act = GC6E22F
Puzzle Containers 9 - Deep Breath = GC6FR68
Puzzle Containers 10 - 1,2,3 The Key is the Key = GC6JNEZ
Puzzle Containers 12 - Pipe = GC6W4C5
Puzzle Containers 13 - Dexterity = GC70N4E
Puzzle Containers 14 - Choo Choo = GC74NGV