As an amateur musician who has been playing the guitar for around two decades there's always been a disconnect between hearing the music and playing the music. Being that I don't really read music very well the only real option has been tablature.
For those who haven't delved into the world of tablature, let me illuminate the situation for you. Back in the day before we had the iTunes music store, we downloaded our music illegally. In those days we didn't really know what we were getting with regards to the files we were downloading until it was done and we played it. Tablature is very similar these days though, admittedly, without the long wait for the download to complete; until you play it it's hard to tell how accurate it is.
I downloaded an application from the Mac App Store yesterday called Capo 3 which claims to show you what chords are being played in the song loaded. This is a pretty bold thing to say. I was skeptical but the user ratings were quite high and, honestly, it wasn't a cheap application. I did some research online as well and the testimonials for it were pretty good and from a fairly solid group of people.
Unfortunately, whether as a result of the software not being as good as the hype and price or as a result of me not using it correctly, it did not live up to my expectations. I found that it would often list the wrong chords, miss chords entirely or have the correct chords listed bars later than they should have been. I'll be keeping my eye on this application because, when it does manage to meet my expectations, it's going to be a hell of a program.