Butterfly Piano
The Wurlitzer Student Butterfly Piano was a 1930's piano for children that was sub-100 lbs with 44 keys. I've repaired the soundboard and keybed/action on two of these instruments and turned them into modified prepared pianos for performance and sound design.
I've used this instrument on several projects, including a score for a short film called Spark Story.
Composer Aurie Hsu features one in a piece called music box.