I don't know about CSound, but Faust works well on microcontrollers, in fact that's one of its main use cases. Note that Faust focuses more on DSP, synthesis and effects, not so much on sequencing and higher-level music organization. I've found combining Faust (for low level) with any general-purpose language (for high level) works well for a lot of things.

https://faustdoc.grame.fr/tutorials/esp32/