Those keys, both major and minor, are easiest to playThis gets me thinking - major and minor are significantly different (even to non-musicians), but with "modal" music you end up with something that's neatly in between, that easily flips either way. Major and minor are more like opposite poles on a continuum than discrete entities.
Flipping between major and minor would probably be expressed by "accidentals" in musical notation, but in a way this is cooking the books to make the notation work.
And here's the thing -
the same applies to keys in general. Guitar is a good instrument to "suss" this one: the chord Gsus4, for instance, is somewhere half-way between G and C.
I could be playing a song that is officially written in G or in C, yet the chord that fits that song best overall is Gsus4. You can't say "this music is written in the key of Gsus4" as there's no way to express that in standard musical notation - it's nonetheless meaningful, and also
very useful to musicians aware of other chord-shades that they've found to work well with Gsus4.
Musical notation, like language, is a convention that enables understanding and communication. But marvelous as it is, it's still just a finger pointing at the moon - and it shouldn't be confused with a reality where its rules don't necessarily apply.
Errr IMHO
