The term 'Organ Pieces' can be broken down into two crossword solutions: STOPS (5 letters) and PEDAL (5 letters). STOPS refers to the knobs, buttons, or levers on a pipe organ that are used to control the volume of the sound. PEDAL is the foot-operated lever on a pipe organ that is used to control the volume and pitch of the sound. Both STOPS and PEDAL are essential components of a pipe organ, allowing the organist to create a wide range of sounds.