Question

Why does consonance have a higher quality of sound (timbre) than dissonance?

Answer 1

The intervals we regard as consonant (octaves, fifths, thirds etc.) are (a) culturally determined (b) whole number ratios of frequencies in Western music.

Explanation:

An octave is a doubling in frequency (2:1), a fifth is a ratio of 3:2 a fourth is a ratio of 4:3, a third is 5:4 etc. in the major keys anyway.

What I find fascinating is how in music from other cultures, different intervals are perceived as ‘natural’ or harmonic.

Answer 2

Thought of a secondary effect on re-reading this, but it maybe small.

Explanation:

The whole number ratios described above will cause harmonics to be set up in the adjacent strings/tubes of the instrument. This will give a greater richness, or fullness, timbre as you might say!