There's so much variability in tonal systems, I don't think we can make any kind of claim about "natural".
Western Europeans are used to an 8 tone system that's been even tempered. Move away from that at all and it sounds weird to most people. Even what most people think of as classical would sound odd to them in their original un-tempered forms with contemporaneous instruments.
Hell, most people don't know what to make of minor chords, let alone something like pentatonic systems or even more "weird" to us tonal systems.
Professor Greenburg discusses this in "How to Understand Great Music" (if I remember right), which is in many libraries (It's a Teaching Company production, which are university courses on DVD). He's a fantastic presenter, very honest and direct about how music has developed.