MIDI Guitar for GarageBand is a Mac app (remember those?) that turns your guitar into a MIDI controller for, well, for any instrument you like. Thus you can thrash away on your axe like the heavy metal rock god you are, and have the sound emerging from the speakers be a plinking, ringing triangle.
The app works by analyzing the guitar’s output and turning it into a MIDI signal, and developer Lukasz Paczkowski says that it even works with chords. I have used a guitar midi controller, and it was a lot like the guitar controller you use for Guitar Hero, with flabby plastic strings and no real physical feedback (this was in the 1980s, though, so things are probably a lot better now).
However you look at it, this is a cool idea. Instead of buying an expensive controller, you can just cough up $0 to try the app (a $40 in-app purchase kills the ads) and use you own presumably awesome guitar.
And it doesn’t end there: you can also add effects to the guitar before sending the results to GarageBand.
Source: Jam Origin