People with little or no theoretical training often have the deepest insights into musical line, provided they are given free rein and are unafraid to open their mouths and sing. What they sing -- i.e., how they tune pitches in relation to one another -- is most of the time amazingly revelatory of the inner dynamics of pitch relationships.

I learned this from reading back in the 1960's Viktor Zuckerkandl's splendid study Sound and Symbol: Music and the External World. The study, now considered dated in the light of current fashions in scientific inquiry into musical phenomena, is all about the inherent sense of tone and how it is revealed by people's response to it.

The two sight-singing groups I now lead are actually tuning classes. In each the quality of the singing is, if vocal quality is the standard, mediocre. The quality of the musical experience has been for some of the participants life-changing and it never is anything less than extraordinary in what it reveals about the inner workings of tone.