[Gloin the Dark]

Major chords sound pleasing primarily due to physics and acoustics

I’m sceptical about the idea that notions of consonance or “pleasing” harmonies are primarily due to these physical properties, or the simple mathematical ratios which give rise to them, even though these clearly play a key role (no pun intended).

For one thing, there have been (or so I’ve read) examples of musical cultures in which these intervals – even the octave – are not regarded as being as natural, consonant or pleasing as we generally think of them, even though the mathematics and the physics are identical in these cultures.

For another, there are intervals that we hear as consonant but which do not correspond to particularly simple ratios. The most striking example is the (12 tone equally tempered) minor third – indeed, one of the component intervals of the major triad – where the ratio of the two pitches is the fourth root of 2: a number which is not close to any rational number as simple as 6/5 or 7/6, and yet which produces an interval which is more familiar and natural to us (or at least to me!) than the just minor third (ratio 6:5) and certainly than the septimal minor third (7:6).

My default assumption is that our notions of consonance come from certain culturally constructed expectations and habits, and are not intrinsically determined by mathematical or physical properties, but that the mathematical properties of certain intervals can give rise to physiological features which make them more easily recognisable to our perceptual faculties, and that this in turn gives them a much greater chance of becoming important players in any culturally constructed musical language, and hence of sounding “pleasant” to the people steeped in that culture.

Thus the perfect fifth (3:2), though it has a high chance of becoming a harmonious interval, is not guaranteed to, just as the minor third is not prohibited.