The hardart was allegedly invented by P.D.Q. Bach and is featured in the Concerto for Horn & Hardart. The hardart uses different devices, such as plucked strings, blown whistles and popped balloons, to produce each note in its two-octave chromatic range. The name “hardart” and the name of the concerto is a play on the name of proprietors Horn & Hardart, who pioneered the North American use of the Automat. Like the automat, the hardart had small windows in the front where the musician had to insert coins to remove implements needed to strike or otherwise play the devices that produced the notes.
—based on the Wikipedia article on the Concerto for Horn & Hardart
