@John I use (the sadly late) Paul Hudak's [Euterpea](http://www.euterpea.com/). Paul's [original paper](http://haskell.cs.yale.edu/wp-content/uploads/2015/03/HSoM.pdf) is worth reading. Outputs include [Lilliput](https://musescore.com/user/27052214/scores/4874469) scores and midi devices. I don't know what soft synth windoze folks use. I use Fluidsynth which is linux/mac.

Trying to link to the Euterpea github account I came across [Sonic Pi](https://sonic-pi.net/) which looks interesting.