Petrof Inharmonicity

[dpitsch]

OK you owners of RCT, how are the readings for S&S, M&H, Petrof for
inharmonicity?

Mike Swendsen wrote:

> I know there has been a lot of talk about inharmonicity, it being higher or
> lower than average, and quite frankly, I think that what is being listen to
> is not the in harmonicity of the instruments is question.
> If you listen to the tone of a S&S for instance it is quite complex ( read
> many harmonics, and most of them towards the high end) and with a Petrof
> those very high harmonics are not so prominent,  on the other hand the lower
> harmonics are.  This gives the piano a very clean and clear sound, I have
> heard some people say 'bright' but that isn't quite correct.  A Steinway or
> a Mason and Hamlin are bright, I.e. there is a strong sense of  higher
> harmonics.
> It would be interesting to have someone with a good frequency analyzer test
> these pianos, and show the results.
> As far as the 'stretch' numbers on Petrofs go, they almost always fall
> between 5.5 and 6.0
> C. Mike Swendsen RPT
>
> -----Original Message-----
> From: Billbrpt <Billbrpt@aol.com>
> To: pianotech@ptg.org <pianotech@ptg.org>
> Cc: cvandenhandel@aviall.com <cvandenhandel@aviall.com>
> Date: Monday, March 02, 1998 9:56 PM
> Subject: Petrof Inharmonicity
>
> Dear List:
>
> I received this question from an outside reader about inharmonicity in his
> Petrof piano.  I think it would be best responded to by the List, especially
> those who are in the manufacturing and rebuilding end.  I'll explain my
> limitations in my response following the question.
>
> <<Subj: Petrof Inharmonicity
> Date: 98-03-02 10:38:49 EST
> From: cvandenhandel@aviall.com (Cornelius Van Den Handel)
> To: Billbrpt@aol.com
>
> Dear Mr. Bremmer,
>
> I read your technical notes in the PIANOTECH archives with interest.  As an
> engineer, I'm intrigued by your description of pianos in terms of their
> inharmonicity, with the Steinway's and the Kawai's on the higher and lower
> ends of the inharmonicity scale.  I own a Petrof 7'9" grand which I
> purchased
> new three years ago.  If you have any experience with the Petrof designs, I
> would be very interested in whether you consider them to be low or high
> inharmonicity.
>
> Also, I spent some time in the local showrooms this weekend, and had the
> opportunity to play new 7' Mason & Hamlin -- how would you describe its
> tone?
>
> To see if I'm at all close, I'd say that the M&H is on the higher end of the
> scale, probably less than the S&S B I played yesterday.  The tone of my
> Petrof
> seems less complex than the S&S, too, so I'd guess its inharmonicity is
> moderate to high.
>
> Cork Van Den Handel>>
>
>     I have to admit that I really do not know what role inharmonicity plays
> in
> tone.  I have come to understand quite a bit in recent years what effect it
> has on tuning as far as temperament and octaves go.  The fact that there is
> inharmonicity means that an octave must be greater in width than is
> theoretical (1200¢).  This also means that all 3rds are wider and all 5ths
> which are tempered must be tempered less than theoretical.
>
>     The SAT and Reyburn programs used with ETD's effectively stretch an ET
> out
> to meet the calculated inharmonicity a piano has.  Sometimes these programs
> do
> not produce results which are entirely accurate because the pianos scale
> design is not uniform.  Sometimes a combination of two programs solves that
> problem.
>
>     While I choose not to tune in ET, I still take a sampling of the
> Inharmonicity a piano has the way Dr. Al Sanderson originally invented.  I
> take a reading of the difference between the way the note F4 reads when read
> on octave 5 and then on octave 6 (this is the difference between the 2nd &
> 4th
> partials).  This was called the "stretch factor" with Sanderson's first
> program which was known as a "stretch tuning".  Later, he developed a more
> complex program that takes 3 samples.  It is the FAC program you will often
> see mentioned on the List.
>
>      I don't need any more than the sampling from F4 for my purposes because
> I
> only need to have a sampling from the temperament octave to know what sizes
> of
> intervals I will construct.  I construct all of my programed tunings by a
> combination of calculated interval sizes, direct interval construction and a
> method known as "equal-beating".
>
>      The "stretch factor" number of most pianos comes out to be between 3 &
> 7
> with a number somewhere in the range of 5 being average.  When I figured out
> a
> way to program an SAT to produce any of the Syntonic Meantone Temperaments,
> I
> found that I was limited to only 3 choices.  Therefore, I had to decide
> whether the piano's scale was "low", "medium" or "high" inharmonicity.
> These
> descriptions are mine and not any manufacturer's nor do they come from any
> other source other than what I just described.   A number of 3 (or below) to
> 4.5, I consider to be low, from 4.6 to 5.8, I consider to be medium or
> moderate, 5.9 or above I consider to be high.
>
>     I have consistently found Steinways to be in the high range, usually
> right
> about 6 but I have seen them as high as 7.5.  Yamahas, Young Changs and
> Samicks are always in the moderate range.  I have always found Kawais to be
> low but once I found a 7 foot model to be on the low end of medium.
> Baldwin
> concert grands are low but the parlor grands are medium.  Acrosonics are
> high
> but their wound string section doesn't seem to match the tenor.  This is one
> of the pianos where two FAC programs need to be used.    Mason & Hamlin and
> Sohmers are always low.  These two are well known as parlor pianos and
> usually
> have a deep, rich but mellow tone.   Kimballs & Kohler & Campbells are
> always
> high (very high).
>
>     I seldom tune a Petrof.  I did one grand just before Christmas but I
> honestly don't remember what its value was.  I would guess it was on the
> high
> end of moderate and possibly high.
>
>     Again, I don't really know what role inharmonicity plays in tone or its
> complexities but if you ask me, I would always want a high inharmonicity
> piano
> like the Steinway for a piano concerto.  The high inharmonicity allows
> greater
> stretching of the octaves without introducing any distortion in them.  This
> allows the piano to compete with the string sections who have a tendency to
> push the pitch upwards and make the piano sound flat in comparison.  When
> tuning a 1/7 comma meantone temperament, which has only a slight wolf (a
> wide
> 5th between Ab & Eb), a high inharmonicity piano will naturally produce a
> less
> dissonant wolf than a low one will.
>
>    On the other hand, a low inharmonicity piano makes a seemingly more
> appropriate choice as a chamber or parlor piano.  Of course, Baldwin and
> Kawai
> concert grands sound great as concerto instruments too and Steinways sound
> great in living rooms.  It still helps to know what general range a piano's
> inharmonicity falls in in order to manipulate a tuning for a given
> situation.
>
>    If there is anyone on the List who tunes a Petrof regularly and uses an
> FAC
> program, he/she may be able to tell you whether the figures seem low,
> moderate
> or high in comparison to most other pianos.
>
>     Thank you for your interest,
>
>      Bill Bremmer RPT
>      Madison, Wisconsin