How To Choose an ETD was ... something else

[John M. Formsma]

David,

I rate the intervals in this order of importance: unisons, octaves, double
octaves, 12ths, etc. (Naturally, the width of the temperament octave(s) will
determine your 3rds, 4ths, 5ths, and 6ths in equal temperament. I didn't
include them in the above list because they aren't as quickly noticed like
the others when one is playing music.)

I was noticing 15ths (double octaves) beating too fast, particularly in the
upper bass of many consoles and spinets, and occasionally on better-scaled
pianos. (This was even in the Clean style which has the smallest
pre-programmed stretch.) Somewhere around 1-2 bps, which is too fast - makes
the bass sound flat during normal play. 

The 15ths are proportionally related to 12ths in Equal Temperament.
Therefore, most of the 12ths were nearly pure in the bass, or wide in some
cases. It's better to balance them out by reducing the size of the octave,
which inevitably reduces the 15th and the 12th. This way, there is only a
slight beat in each interval. More balance. 

In the treble on most pianos, the 12ths were a bit too narrow, except when
modified by the stretch settings. Depending on the piano, the stretch
settings were somewhat unpredictable as you had to tune most of the piano to
find out how things were going to turn out in the treble. Almost 1 bps in
many pianos, which is not bad, but they could be better balanced by slightly
expanding the 15th. This makes both the 15th and 12th beat about 1/2 bps.
Sounds good that way. The octaves, twelfths, and double octaves sound pure,
even though they are not technically pure. 

In some pianos, some tenor 4ths were beating 2 bps, which is not acceptable
in ET. The audible 4ths normally need to be around 1.0 in the lower part of
the temp octave, ascending up to 1.3 bps in the upper part of the temp
octave. You can push this "limit" in the larger pianos, and the piano will
tell you what it wants.

I find one must begin with an octave that is between a 4:2 and 6:3 to get
the best balance in most pianos. Larger concert grands don't have as much
difference, and small consoles might require a just 4:2. It requires
listening to how the two notes blend together for the optimum sound. Then
squeezing the rest of the intervals into that octave, then expanding that
octave into the rest of the piano.

Hope this answers your questions.

John Formsma

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of David Ilvedson
Sent: Monday, May 22, 2006 10:01 AM
To: pianotech at ptg.org
Subject: RE: RE : How To Choose an ETD was ... something else

John,

Maybe you could explain what "make the more important
intervals sound better: e.g., the 15ths, 12ths, and even 4ths on certain
smaller pianos."   What is "better" in a 15th?  12th?  4th?   

David Ilvedson, RPT
Pacifica, California