Here are some backing tracks I created with only drums and fender rhodes which can be used to practice bass guitar (or synths, guitar, whatever you wish).
https://www.youtube.com/playlist?list=PLNtBwe-YZVg_VACloz6pzYXFVFc5SuDCY
The vibe is mostly easygoing funk/swing/jazz/lounge/pop/hiphop...