[pianotech] Sustain

[Ron Nossaman]

Porritt, David wrote:

> I’ve been in classes on voicing where people talk of hammers that 
> enhance sustain, or show how to voice the hammer to enhance sustain.  
> They’ll do their thing to the hammer and proclaim that the sustain is 
> longer and the whole class nods in agreement.  I’ve never been sure if 
> this is a real, or a psycho-acoustic phenomena.  Has this every been 
> actually measured with lab equipment?  I haven’t figured out the physics 
> of this.  What can the hammer do – however it is made or voiced – to 
> keep the energy in the string and lengthen the sustain?  I understand 
> that we can change the prominence and number of the partials by voicing 
> or by changing hammers, but can we actually make the string vibrate longer?
> 
> dave

I ran into a wonderful example of this earlier this year. A 
Petrof vertical, owner complaining that the sustain had 
dropped way off in the last year. I played around with it for 
a while, and found what I thought was the problem. Did some 
voicing in a small area and had him critique it. "That's it! 
What did you do?" I showed him a section I hadn't voiced and 
we compared. The tonal envelope in the "short sustain" section 
had a sharp short attack spike, with the dwell and decay 
considerably quieter. The impression, even though the total 
duration was similar, was that the sustain was short. What 
worked best on this piano was side needling high shoulders. I 
had him listen while I worked a hammer and he could hear the 
attack peak lessen, and extend further into the tonal 
envelope, blend more smoothly with the dwell and decay. The 
impression was a longer sustain, but it was just a 
redistribution of the power curve. This is, I think, a lot of 
why hard hammers in capo sections of grands often seem to kill 
sustain, where a little voicing will help.

That's my story.
Ron N