Can you answar a question about modes? I was listening to Back in black by ACDC and found the intro chords E5-D5-A5 over this progression they play Eminor/Gmajor pentatonic shape I in the first riff in the intro. I figured out that the song is in the key of A and a V,IV,I progression with E minor pentaton elements, is this to be called a mixolydian song or is it a blues based rock song or something else?
The main progression to "Back in Black" by AC/DC is indeed Mixolydian mode. But Angus Young is mostly a blues-based rock player and usually opts for the minor pentatonic scale for his lead guitar solos. This song is no exception. You do hear him go a bit outside the box at the very end of the solo. E D E, D C# D, C# B C#, etc. These notes are derived from the parent A major scale and create the Mixolydian modal scale.