On the 8 UK albums that Jones played on he played the following:
'Rolling Stones': Guitar, harmonica and percussion
'Rolling Stones 2': Guitar, keyboards and harmonica
'Out of Our Heads': Guitar, harmonica, organ and percussion
'Aftermath': Guitar, harmonica, marimba, bells, Appalachian dulcimer, sitar, koto, keyboards, percussion
'Between the Buttons': Guitar, piano, organ, electric dulcimer, percussion, harpsichord, kazoo, recorder, theremin, trumpet, trombone, tuba, saxophone, harmonica and sitar.
'Their Satanic Majesties Request': Mellotron, keyboards, electric dulcimer, recorder, percussion, theremin, concert harp, sitar, saxophone, flute, brass, bass guitar
'Beggars Banquet': Guitar, harmonica, mellotron, stiar, tamboura
'Let it Bleed': Autoharp, percussion.
So I make it 26 in total, or 28 if you count electric, acoustic and slide guitars as separate instruments. He is also credited with doing baking vocals on most of the above albums.
- all the above information was taken off those albums' wikipedia pages which are all linked to on this page:
https://en.wikipedia.org/wiki/The_Rolling_Stones_discography#Studio_albums