On Mon, 19 Jan 2004 09:42:43 +0000, Chris Isbell
wrote:

No, I could go on at great length about tuning and pitch. ;-)

The question I was trying to get at was that it the chain from the
instrument to my ear/brain is substantially linear, then why do I hear
beat frequencies? (If it is not linear, then why is linearity such a
concern for Hi-Fi systems?)

How did we get sidetracked into this "linear" argument?

You hear beats because they are a simple physical result of mixing two
sounds of close pitch. That's it.

If you set up a series of pitches approximating to the overtones of a
low note, your brain will sometimes "hear" the low note. This isn't
mumbo-jumbo, it's an established technique in church organ
construction, and probably elsewhere. But it's nothing to do with
beats.