I think JimmyM said it above the best. However per Phatbass's post, if you really want to learn the parts learn it slow. Maybe invest in a Slow Down Trainer like the Tascam GB-10 or if you have an iphone or iPad tryout the Slow Down Music Trainer app
I took your advice and bought Irehearse app. it is really awsome songs that ive always wanted learn to play by ear like for instance Rush's "ANALOG KID" I always wanted to learn that song by ear! i had no idea that there were that many notes being played in that opening riff! it is an awsome app it slows down the song but doen't change pitch of note! and you can put it on a continuous loop until you get it! its a great app i recomend it! so i run through that riff a couple of times to work on my speed and acuracy!