​INSTRUMENT, in law, a document or writing, as the means of giving formal expression to an act; a writing expressive of some act, contract, process, or proceeding, as a deed, a contract, a writ, etc. In music, any mechanical contrivance for the production of sound. The musical instruments employed are divided into the following classes: Stringed; wind; and pulsatile. The first and second class require no description. The pulsatile or percussion instruments are the kettle-drums, great drum, side drum, triangle, cymbals, and tambourine.