At a gathering of early music folks there will always be people who specialize in a cappella singing. I don't specialize in it; I am utterly fascinated by it.
The difference might be summed up in the title of this post. I believe that tuning voices involves a sensation of natural harmonics coming into focus. I have had better luck achieving this with amateurs who know nothing about singing and very little about music than with trained musicians.
I suspect the reason is that, once trained, musicians learn to expect what they will hear rather than allow themselves to hear what they actually do hear.
Perhaps this is reason so many early music people dislike the modern piano: they expect a D major triad to sound like a D major triad on some properly tuned harpsichord, while I am utterly fascinated with its chaos relative to, say, the E-flat major triad.
