melodeon

noun3

1. •
   An accordion where the melody-side keyboard is limited to the notes of diatonic scales in a small number of keys.

   • 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. — 1932
2. •
   (historical) A type of reed organ with a single keyboard.

   • 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. — 1909
3. •
   (US, historical) A music hall.