melodeon

1. (historical, music) A type of reed organ with a single keyboard.Examples: "The thin, nearsighted young woman who had been humped over the keyboard of the melodeon, straightened up. The worshipers relaxed a little and began to look about."

2. (music) An accordion where the melody-side keyboard is limited to the notes of diatonic scales in a small number of keys.Examples: "But Chae said it didn't matter, he'd bring his melodeon and Long Rob his fiddle; and faith! if that didn't content the folk they were looking for a church parade of the Gordons, not a wedding."; "His brother, Roy, joined him as a dancer - their two-man jigs were much admired - and his nephew, Jamie Wheeler, has become the side's principal musician, on melodeon and fiddle."Synonyms: diatonic button accordion