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. Because of its high pitch, it could be heard over the activities of the crew and bad weather. It is now used in traditional bugle calls such as Evening Colours / Sunset.
Piping aboard: When flag-rank officers or an important guest is boarding a Navy ship they had to hoist them up using a bosun's chair when the weather was too rough for the use of ladders. The bosun would use his call to direct the side boys in the hoisting of the chair.
The following are some commands given by the bosun's pipe.
Hauling a line, rope or anchor.
Lowering a bosun's chair.
Away boats, to order a boat to leave the ship's side.
Call the Boatswain's mates.
All Hands on Deck.
Command for silence, an order to follow.
Pipe down, a dismissal of all the crew not on watch.
Pipe to any meal.
Carry on: dismiss the crew back to their duties.
