Obsolete musical instruments

There are a great variety of other instruments that have been made that are no longer around. Here are some examples:

• Basset Horn: a single reed instrument that was often bent in a variety of shapes then sent through a soundbox
• Natural horn: an older version of the horn which uses a series of tubing extensions which attach at the mouthpiece hole
• Racket: a double-reed instrument that sends the sound through a series of waves to deepen the sound
• Saxhorns: Adolphe Sax developed both the woodwind saxophones, and an odd variety of brass instruments called "Saxhorns"
• Theremin: an electronic instrument that is played by moving ones hands around
• Valve trombone: apparently these instruments exist, but I've never seen one
• Viol: an early form of the violin
• Wagner Tuba: a tuba-like instrument that is played and built like a horn, mainly of course used by Richard Wagner

There are a great many others, but this is a start.