Boatswain's call

The pipe consists of a narrow tube (the gun) which directs air over a metal sphere (the buoy) with a hole in the top.

The player opens and closes the hand over the hole to change the pitch.

The rest of the pipe consists of a "keel", a flat piece of metal beneath the gun that holds the call together, and the "shackle", a keyring that connects a long silver or brass chain that sits around the collar, when in ceremonial uniform.

Historically the boatswain's call was used to pass commands to the crew when the voice could not be heard over the sounds of the sea.

It is sometimes accompanied by other auditive features such as ruffles and flourishes, voice commands and announcements, or even a gun salute.