[pianotech] ETD stretch vs pure (octaves)

[Richard Brekne]

I understand what you are saying Duaine... but the point is that if you 
listen closely enough, you actually DO hear beats and wave-y-nes no 
matter what you do. Its just that at some few sweet spots you get an 
illusion that there is a pure octave. The dominant coincidents for any 
given octave can be brought into line well enough for this to happen in 
much of the middle part of the piano to the degree one has to listen 
fairly closely to notice the beating in the whole coincidents partials 
ladder.  But in the extreme ranges... not so extreme actually as one 
moves down into the bass region... the mesh of beating coincidents along 
with those that are either beatless or very close to being is very 
noticeable.

The <<pure octave>> is only an illusion. All the comments about 
coincidents I've read in this thread so far are pretty much right on 
target. I think perhaps we are getting hung up a bit in semantics ?

Cheers
RicB


    To me, a pure octave is when you play C4 and C5 together, and hear no
    beats or wave-y-ness.

    Just like tuning unisons of a tri-string and they are in tune when you
    hear no beats or waves, except they are an octave apart.

    If C4 is in tune and you hear beats, that means C5 is sharp or flat.