pipe is a whistle-like device used to tune a musical instrument or to give a reference note to a singer to ensure that they sing in the proper key
. It can also be used to activate electronic devices that are sensitive to specific audio tones.
The pipe is made up of as few as six (for simple guitar tuning) to as many as thirteen (to cover the semitones through a complete octave from C to C) metal tubes, bound in a row and staggered in length so that they protrude with room to blow into each without coming in contact with the next tube.
Much less expensive than an electronic tuner, a pitch pipe does require a decent ear.