Watch the Angus Young online guitar lesson by Jeff McErlain from Kings of Tone
Angus plays hard and with a lot of aggression that contributes a lot to his tone. He picks hard and that in itself makes the amp distort a certain way. So when learning this solo try playing it softly and hard, you will hear the difference right away. This is especially important when working with more vintage amp sounds, the pick attack has a greater effect on the tone and gain than it does when playing a really saturated compressed tone. The gainy tone loses much of the dynamics created by the pick and for a player like Angus that's a huge part of his sound.