Hi Lee,
I’ve now worked through the entire Guitar Theory book and feel I’ve got to a better place to understand and break down many parts of songs. I have a question that is quite general regarding many of the 80’s rock and hair bands type of music.
The song I am working on in transcribed with a key signature of A (3 sharps). The intro begins with a riff using D5, A5, G5, D5 repeat and then the verse goes into A5, D/A, G/A, D/A, A5
Overall the tonality is definately A, and thats where the opening riff seems at rest. If its transcribed in the key signature of A, and the tonality is A, the opening riff is IV, I, bVII, I. I don’t understand why the G is not a G#. It sounds better as as a G, and many early AC/DC songs are use these three chords (A, D & G) and are in the key of A, but if the key signature is A, why is the seventh chord flattened. As you mention in the text, many people say its Mixolydian – but that does not seem correct! I thought perhaps the song would have better been transcribed in C with an A tonality (relative minor) and that fits because all the chords are essentially V chords.
Cheers
If you wanted to stay strictly in A major then the vii chord would be G#dim.
Generally speaking, if you wanted to compose a song that used A mixolydian then you’d more likely use fewer chords and maybe use a drone note to stabilise the key. The underlying relative major key of A mixolydian is D major so you could use any of the chords from D major. Trouble is, the more of them you use, the more it will pull towards sounding like D major.
If you use A, D, E, G (all major chords) then you’d have a bit of a mix up of keys because for it to be either D major or A mixolydian, the E would need to be E minor.
If you are using 5 chords then things are a bit different because of the lack of the third. So A, D, E, G could belong to A mixolydian or D major as long as at least the E is played as an E5 power chord because it’s neutral, only containing the notes E and B which belong to the key.
Everything else that dictates the tonal centre will just be down to how the chords are played or if any other melodic content is pulling the home key towards A or D etc.
For the most part with rock songs using power chords, if you see it’s based around I-IV-V chords, then most of the time we can assume the key signature is relative to those chords. For example, D, G and A major chords are the I-IV-V of D major. If the tonal centre feels like anything other than D then it’s likely to be based on one of the modes of D major. In this case .. A. If these same chords felt like the tonal centre was E then we’d probably say it’s E dorian, and so on.
I’m not sure I’ve managed to explain that very well so let me know if it makes any sense and we’ll take it form there.
