Digitech Trio band in a box. You play and it will add bass lines and drums.
Works far better than you might think. Bass can be turned down to zero if you only want drums for practice.
Bass is low register so you can get your jazz on by playing in the upper register.
Only used a little at home, selling because I've now bought EZDrummer. Velcro on the bottom.
£60 including Special Delivery postage UK. Comes with the powersupply