Lyre of Ire
The Lyre of Ire (Silver harp in the English localization of Dragon Quest and Dragon Quest III for the NES, while the GBC port in English referred to it as the Shiny Harp.) is an item which summons a monster battle when used outside of battle.
The Lyre is an essential item for completing the game, it's acquisition being one of many tests the player must complete to prove their worthiness. It is located in a treasure chest within the Grave of Garinham. When used, the harp summons a very weak monster in the original NES version, or a monster native to the hero's current location when used in Dragon Quest remakes. The harp can be traded to the man in the Shrine West of Kol for the Staff of Rain. Due to text restrictions in the Gameboy Color remake of Dragon Quest, Silver Harp was renamed to ShinyHarp.
The Lyre is hidden in the back room of Garin's home, which is the precursor to Garinham/Grave of Garinham. It can be found by searching in a specfic spot. Finding the harp is a bit misleading because Garin is located in Cantlin and gives the hero a clue to the harp's location. Cantlin is typically visited after Garin's home, meaning the hero will likely have to revisit in order to collect the harp. The harp serves no real purpose in Dragon Quest III, but can be used to summon monsters. Though the addition of Whistle in the remakes render it a novelty item.