Heward's Mystical Organ

In the World of Greyhawk campaign setting for the Dungeons & Dragons role-playing game Heward's Mystical Organ is a powerful artifact, the creation of the hero-deity Heward.

Description
Heward's Mystical Organ is a massive pipe organ the size of a large room. Playing different keys in specific orders can cause any number of different magical effects.

Dungeons & Dragons (1974-1976)
Heward's Mystical Organ first appeared in the fourth supplement to the original D&D rules, Eldritch Wizardry (1976).

Advanced Dungeons & Dragons 1st edition (1977-1988)
Heward's Mystical Organ was also mentioned in the original 1979 Dungeon Master's Guide. A system to generate magical effects for the musical artifact was given in The Dragon #29 (September 1979) in the "Bazaar of the Bizarre" column.

Advanced Dungeons & Dragons 2nd edition (1989-1999)
Heward's Mystical Organ was detailed in the second edition Dungeon Master's Guide (1989). It was further developed in 1993's Book of Artifacts. It also appeared in the fourth volume of the Encyclopedia Magica series (1995).