have a look at the plug of your mic: is it divided by a small black part into two or three metallic parts?
2 means: mono mic - and a mono mic offers you... right, just mono; no technical way to make a mono signal stereo, eccept you can add some stereo reverb etc. with an audio tool as audicy or garage band.
3 means: stereo signal - you're sure, you connected it correctly? push it DEEP into the iMic; there's a little switch at the side of the iMic - it should show you a mic symbol and a line signal; push it to... ok, that's a NoBrainer ;-)
the rts of your equipment: analog audio (as your mic) and midi are totally different things! midi means just some datas ("... press #C4 for 25milliseconds...") - no "real sound, just the information to some sound processor, what to do.
you cannot listen to midi without somekind of soundprocessor, as a syntheziser, a computer, whatever.
analog sound means: real sound, as coming from a mic, out of a piano, your voice.
there is no way (ok, a very expansive way) to make audio to midi! have a look in Garage band, it shows you grafically the difference between audio and midi files