The term 'Organ Piece' refers to a musical composition written specifically for the organ. The four crossword solutions associated with this term are STOP (4 letters), KEY (3 letters), TOCCATA (7 letters) and PIPE (4 letters). A STOP is a device on an organ that controls the flow of air through the pipes, allowing the organist to select different sounds. A KEY is a lever on an organ that is pressed to produce a sound. A toccata is a type of musical composition that is typically fast-paced and virtuosic in nature. Finally, a PIPE is a tube in an organ that produces sound when air is forced through it.