There should be an obvious way to use mic in Nintendo DS games

Many Nintendo DS games require player to blow into mic, or to actually say something.

DeSmuME (2015) actually supports this via pressing L3, but it's very obscure (and we don't even map L3 to keyboard by default!) and doesn't seem to work reliably anyway.

This can be achieved by having a way to play prerecorded sounds (e.g. a "Blow into mic" button), or to actually use hardware mic if available (and probably only enable it on demand). I'm not sure if libretro/desmume actually supports the latter though.