You can use Audacity (http://www.audacityteam.org) together with Vamp Plugins (http://www.vamp-plugins.org/download.html). Currently there are 2 transcription plugins on this site, by Queen Mary, University of London and by University of Alicante.
But beware, (polyphonic) music transcription is a very difficult task, and it very much depends on the type of music and your task at hand if the output of these algorithms is useful to you or not.
As Andreas mentioned, music transcription is pretty hard to get straight away, so always (maybe not so much with a MIDI controller) be critic of results!
I would suggest Dragon Naturally Speaking. They have various options to accommodate varying needs and software platforms - they do offer an option for MAC. I have found it is a good option because it builds a vocabulary base based on individual needs and usage. I believe it is relatively reasonably priced by American standards though I am not sure in terms of Euro or Pound.