Generally speaking, and in popular music, there are four major tonalities. This includes the three major modes and then the blues. The three major modes stem from the three major chords in a key, I IV V (1 4 5). They are called Ionian mode (I), Lydian mode (IV) and Mixolydian mode (V).
If a chord progression is revolving around the I chord, then playing the parent major scale will produce the Ionian mode sound. If a chord progression is revolving around the IV chord, then playing the parent major scale will produce the Lydian mode sound. If a chord progression is revolving around the V chord, then playing the parent major scale will produce the Mixolydian mode sound.
You can’t change the mode by playing something different over it (there are some exceptions but you need to understand the fundamental modes concept first). Modes are determined by the chord progression and root, not what you play. In other words, if a chord progression is revolving around the I chord, then it’s Ionian mode. You can’t make it something else unless you change the chord progression and how it relates to a parent major scale.
The other possible major tonality occurs in blues and blues-based music. In this style it’s common to play the minor pentatonic scale over a major chord. Obviously, playing minor over major causes some conflicts, but the dissonance and tension in this case can sound very pleasing and is an important part of rock and roll. I explain and demonstrate this in my pentatonic DVD and Fretboard Theory book. Also be sure to check out my free Guitar Music Theory Lessons podcast.
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