Sound effects?

[fire dragon]

I want make in my quest animal,or weather effects.Like rain and example cow's voice.So,I want know can I put mp3 sounds together midis?Jessethe2nd needed voice actors sometime ago,and I start thinking,can I make sound effects like explosion etc.?I only want make some extra sounds,without editing other's midis.
Thanks!

[LavaBall]

Good idea for the next version that I hope it will have costum added sounds not just edit other sounds tough