Flow Jam is a little Python toy I hacked together in an evening that provides some flow-following background jams for when you're really in the zone.
I encourage playing around with the thresholds and falloff to find something that works well for your typing speed and patterns.
Yeah! Take a look at jam_library/flowjam and copy the layout into another directory, tweaking the manifest.json and providing your own audio files.
I've tested with wave and mp3 files, but wave files worked better (in my experience) to create a more seamless loop due to their very simple encoding.