The Tubon is a tube-shaped electronic monophonic instrument with a guitar-strap. It is primary a bass instrument with preset sounds like tuba, contrabass, electric bass etc, and is played staccato. It was made in the late '60s in Gothenburg, Sweden by a company called Joh Mustad AB.
Wow interesting that something like that was around back then if not in sound then by look.
I wonder if this was the first Keytar?