Originally Posted by: Ian HandOK I’ve been thinking about this for quite awhile now: Why does the Pentatonic minor scale or blues scale (which is also a minor scale) sound so good over certain Major chord progressions (e.g. I, IV, V)?

My thoughts on this are that the Pentatonic minor and Blues scale although they both have a flattened 3rd (which makes them minor scales) they do not have a 2nd note. This I think makes them more ambiguous sounding compared to the Natural minor scale, for example, which does have a 2nd note which emphasises the minor nature of the scale.

Anyone else have any theories why these two minor scales sound good over some Major chords?

Let's take an A blues, for example. Easy stuff, I IV V7 . If you play in an A minor pentatonic, it shouldn't sound too horrid because you can get away with implying a 7th chord over the major chord. This means that you can now play g and it will sound good. You can also get away with the minor third now, because it becomes a sort of leading tone due to its relationship with the 7th. One of the most famous jazz/rockabilly licks takes advantage of this. Play C, C#, E, G, A, A with two eighth notes, two sixteenths, and two eighths with a triplet feel to hear what I'm talking about and the kind of relationship.

But if you just continue to emphasize the minor third and don't resolve it to either A or the major third--I'm not sure of how good that would sound. I guess you could also get away with it because the minor third extends the chord further.

What was said above--those scales--are all based around chords. Usually the reason why those hybrid scales work is because they are implying extended intervals of the chord that are consonant, usually past the octave level--i.e. 9ths, 13ths.



So yeah, a long way of saying that your original thought was correct. Pentatonic scales simply are more ambiguous and the tones you use in them serve to extend the chord, rather than becoming dissonant. ((Just try playing a minor 6th over a major chord--it's over!))