“Get Back” by The Beatles is based in A Mixolydian mode (a.k.a. the dominant scale). Mixolydian is the fifth mode so the parent major scale is D. The open chord riff is A for three and a half measures followed by G and D. By number this would be 5 4 1, with the 5 chord A functioning as the root (or tonic). Some musicians like to always call the root chord 1 and then renumber everything from there, but I like to keep it simple and just leave the numbers as they occur in the parent major scale.
This song also includes some blues elements. You can here a minor third of A, C, thrown in for a little off key blues flavor. The guitar solo starts out in A major pentatonic, switches to D major pentatonic over the D chord briefly, but finishes with A minor pentatonic.
Music Theory for Guitar
“Get Back” by The Beatles may be an easy song to play, but it requires some music theory knowledge to understand. It’s important to remember that concepts like modes and blues stem from more fundamental ideas like major scale patterns and chord progressions. Guitar theory is a process. Take it one step at a time.
To learn more about music theory for guitar, including scales, chords, progressions, modes, and more, sign up for a free preview of my Fretboard Theory books and DVDs by using the form on this web page.
Play Until Yer Fingers Bleed!
Mr. Desi Serna (Google me!)
Scales, Chords, Progressions, and More