Every so-called guitar player has some nasty words about the pentatonic scales, but they’re often bullshit. He mostly doesn’t even know what he’s talking about. Usually you got a guitarist that has learned some diatonic greek modes just yesterday, and he already counts himself as pro, disdaining others following closely, biting his heels.
If you start to talk about exotic, anhemitonic, hemitonic, cohemitonic, and ancohemitonic scales, they hear any Greek.
So let’s go ahead and talk about pentatonic.
The Pythagorean pentatonic is quite similar to the diatonic: its minor mode lacks just the major second and minor sixth degrees from the Aeolian mode; and its major mode is behind the Ionian mode just by the fourth and the leading notes.
It means the pentatonic is indeed the path to the diatonic.
On one hand we have the diatonic-budding guitar players, claiming Slash knows only pentatonics; on other hand there are 84-scale teachers defending how wondrously awesome he is, with his incredibly complex scales.
Slash takes advantage of some trivial Blues’ tricks. He uses pentatonic, filling with diatonic degrees when appropriate, but not limited to that. He’s not afraid of the Blues’ chromatic nonharmonic tones.
And not only this.
Something Slash uses a lot is the “thinking vertically” melody development.
Don’t know why, but I’ve seen everyone referring to it as “thinking vertically”, never “vertically thinking”.
In the Blues and the Jazz there are two kinds of melody development: “thinking horizontally” and “thinking vertically”, the first one preferred by the Blues, and the second one by the Jazz.
In the “thinking horizontally” development, the same tonic chord scale is respected across the whole song, enhanced by embellishing tones.
In the “thinking vertically” development, the musician changes the scale key according to the current chord. That’s what Slash does when he seems to use complex scales: he simply switches the key. Nothing trickier than that.
And it doesn’t diminish him! It’s a great approach, you don’t have to pretend something else to make anyone look better. It is what it is.
So take the tricks, learn what things are before you try to jump onto the higher steps.
Also in Medium.