Although seemingly less prominent now in music - the Chapman Stick was a game changer for guitar and bass expression simultaneously.
My introduction to this wonderful and unusual instrument came in the early 1980’s and that trio of wonderful King Crimson records - particularly the “Beat” album and the track “Frame by Frame” with stick playing from the bass legend Tony Levin.

(Tony Levin)
Typically the instrument has 10 or 12 strings with a large central bass string that divides the tuning either side into 4ths or 5ths along its long scale.
The instrument is held by belt hook and strap and the player uses a hammer on and tapping technique to play bass lines and chords simultaneously.
The stick was developed by jazz guitarist Emmett Chapman in the late 1960’s and offers a span of up to 5 octaves.
Active and passive pickup options can also trigger guitar synths to open up a whole new world of sonic capabilities.
I was fortunate to see Tony Levin in action on the stick on the Peter Gabriel “So” tour in 1986 - as well as meet him a few years later where he demonstrated the instrument at close quarters!
As previously mentioned we do not really see the stick that much in popular music - but there was a time in the 80’s when boundaries were being pushed and some amazing records were made with the stick.
Go check it out further!