I loved to build backing tracks for guitar in Band-in-a-box, just from the chord progression and some settings. Leveraged little effort to interesting results. And the idea of a DSL is super. But I dunno how would you stand comparisons with audio rendered by pro DAW software loaded with a production quality sound library such as Hollywood Strings or similar if you render the audio yourself.

Ha, I was just playing with making a simple pad in webaudio and it evolved into a progression-playing backing track tool (vanilla html/js/css page). It would appear there are a lot of us in the Venn intersection of programmer/guitarist/practice time alone enjoyers.

DSL for backing tracks: https://github.com/ako/backing-tracks