I recently revisited and listened to an old recording of me doing some jazz improvisation on the piano.
I was teaching myself how to read music for the piano and most of these are exercises I was doing to follow along with the Music Theory by Hal Leonard book I was studying from.
To create these tracks I used 3 pieces of equipment: Roland SP-606, Axiom49 MIDI Keyboard and Logic Pro on iMac.
I'd come up with a little jazzy drum loop using the Roland, then open up Logic Pro and find the grand piano. I'd loop the drum loop for 2-4 minutes and hit record, and then do some piano improv over the drums.