1. What is the difference between the diatonic and pentatonic scales?
This is a great question on guitar music theory. The term diatonic basically means two tones. This refers to the two different types of steps that occur on the main scales, full step and half step. The word is also used to indicate when something comes from a key. For instance, “this riff is diatonic” means that all your notes come directly from the main major scale. Gold, “This guitar solo is not diatonic” means that it presents notes that are not part of the main major scale (such as chromatic step tones).
Pentatonic scale patterns are not considered diatonic because they are not based on a two-step formula. And they don’t have seven notes like the major scales.
2. How can I play a major pentatonic scale over a song that uses major scale chords?
The pentatonic scale follows the root chord in a progression. The root is the tonal center of a song and usually where everything begins and ends. If the root chord is major, you can play the same major pentatonic scale throughout the progression. If the root chord is a minor, you can play the same minor pentatonic scale throughout the progression.
For example, the song “Wonderful Tonight” by Eric Clapton is based on a 1 5 4 5 chord progression (GDCD) in the key of G. The G chord is the root as it all comes close to and resolves into he. Therefore, you can play G major pentatonic scale patterns throughout the song. Just place pentatonic pattern one so that the second note is G (the relative minor is E).
Led Zeppelin’s “Stairway to Heaven” guitar solo is based on a 6 5 4 chord progression in C, with the 6 Am chord functioning as the root. So you can reproduce Am’s pentatonic scale patterns throughout the progression. Just place pentatonic pattern one so that the first note is A.
To use the correct major scale, you must take into account the entire progression, not just the root. So in the first example, play G major scale patterns. In the second work, C major scale patterns (Am is the relative minor).