I've often said that guitar is a minor instrument; however the other day someone called me on that and asked me to explain it.
You see, that's why the minor guitar scales sound best (in my humble opinion) on the guitar.
Not that other scales don't sound good, but the minor ones sound great, and they have the added benefit of just lining up great, fingering-wise.
Have you ever noticed how the minor pentatonic or diatonic scale pattern has that row where all the notes on the one fret are used?
That's not by accident folks!
So, WHY is the guitar minor?
Well, look at the notes of the standard E tuning: E-A-D-G-B-E
What chord do those notes form? (Didn't think that was a chord? Gotcha.)
Well, the E, G and B form an E minor chord. The second E is a repeat, so we don't worry about that. The D is a 7 in relation to the E, which means that so far we have an Em7 chord.
That just leaves us with that pesky A...
Well, A is a perfect fourth of E, and as such it can still work in the chord. The only weird part is that given its low octave, it muddies the sound a bit. (Try an Em7 with a higher A over top, and it will sound great).
So that leaves us with an Em7+4
Hence why the guitar is a minor instrument.
To learn more about the number system that governs all this stuff on the guitar, checkout my Unlocking I IV V course - that's the kind of stuff you can have a handle on in no time flat.