[pianotech] Sustain

[David Love]

The length and quality of the sustain phase is clearly complex but I think
it breaks down into three areas:  soundboard, string, hammer.  The manner in
which the soundboard first captures energy from the string and the rate at
which it dissipates it is fixed by the nature of the assembly itself in
terms of both stiffness and mass.  In simple terms, the stiffer the assembly
or the more mass it has the greater the amount of energy required to move it
but the longer it takes to dissipate the energy.  The amount of energy that
can be stored and made available for transduction to the soundboard is a
function of tension and mass of the string.  The manner in which the string
is set into motion influences the way that the string divides, the amount of
energy lost by virtue of initial chaos in the attack phase and the point in
the phase that all the divisions become consonant, achieve their maximum
amplitude as well as the amplitude itself.  All we can really influence in
the voicing or toning process is the manner in which the string is set into
motion, the initial loss of energy in the chaos phase, the point in
development when the chaos is turned into divisional consonance and the
distribution or strength of the harmonics.  So hammer manipulation is
certainly not without consequence but whether it actually influences the
length of sustain I'm not convinced.  The quality of the sound especially in
the beginning development phase is what we hope to effect and that certainly
can change our perception of the quality of the sustain phase.  The absolute
endpoint of the sustain I don't think really changes with any manipulation
of the hammer since at that point of low energy input it is the soundboard
itself combined with the string's ability to store energy that is
responsible for when things come to rest.  That's how I view it anyway.  I'm
sure there's a better and probably more accurate scientific explanation.
>From a perceptual viewpoint there is also the issue of what I've heard Del
Fandrich refer to as "usable sustain" meaning the sustain that we actually
hear musically as opposed to what might be measurable.  The usable sustain
might well be considered in two ways: first, the ability for the system
(string and soundboard assembly) to store energy and the rate of decay; and
second, the shape of the decay curve itself.  While the first factor is not
influenced by the hammer the second is and the shape of the decay curve
certainly can influence our perception of the usable sustain.

The swell effect when you lift the damper comes, in my view, from the
growing sympathetic excitement of the strings that have been freed from
damper constraint.  

David Love
www.davidlovepianos.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of John Delacour
Sent: Wednesday, December 31, 2008 7:25 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Sustain

At 08:29 -0500 31/12/08, Marcel Carey wrote:

>I'll risk my 2¢ here. I don't think it's only  an impression of more 
>power that you get with voicing. I think that proper hammer voicing 
>can really increase the amount of energy that goes into the string 
>and soundboard system. Here is My reasoning...

I won't speculate as to the reasons, much though I'd like to 
understand them, but I agree that it is not simply an aural illusion. 
Sustain can be measured in seconds from measured blow to silence, so 
it's easy enough to put any fantasies to rest.  In the case I 
mentioned there was most definitely a considerable increase.

There are also pianos, usually very good ones, which exhibit a swell 
in the volume just after the attack and then a smooth decay.  I'd 
like to know what happens here as well, and there are rather rare 
pianos which exhibit a marked swell if the dampers are lifted after a 
held chord is played.

At 19:31 -0800 30/12/08, David Ilvedson wrote:

>A little more explanation of what you did...?

Nothing very different from what I normally do.  We all have our own 
special ways of toning and a lot too much mystique is built up about 
the technique of toning.  Anyone can jab needles into hammers but not 
everyone can hear, as a recent thread has demonstrated.  In toning 
one needs to be able to identify and focus on any part of the tonal 
spectrum in isolation or in combination.  I always use a single 
needle and most of the groundwork is done with a stabbing action with 
the hammer heads supported on a little rosewood tray.  As the work 
progresses I also use a squeezing or pushing action, which I use 
exclusively for the una corda toning.  As to the crown, I work with a 
fine 3M Fre-cut 618 paper and a polished steel rod.  I never jab 
needle into the crown.

JD