Key Leads and Inertia

[Richard Brekne]

Stephen Birkett wrote:

>
> Ric suggests getting some real data:
> >One point I'd like to get clear pretty quickly tho... just what
> >level of play can we expect to be able to expand the so called soft
> >zone too by configuring the keys intertia appropriatly ? Is this
> >limited to some level of pianismo ? Or can this feasably include mf
> >perhaps even forte play ? I must admit I've not really thought of
> >these musical concepts for play level in terms of actual input force
> >in grams.
>
> Sure. It wouldn't be too hard to estimate some parameters for real
> keys and actions, get some idea of the musical ballpark we're playing
> in. In a real action the parameters all change with the stroke, in a
> nonlinear fashion, but fixed estimates would still be valuable and
> consistent with the high school physics approach taken in the little
> article. I'll think about the numbers a bit and report back.
>

I did a little very informal playing around with a digital 0-5 kg scale
yesterday, and very very roughly, a light touch held the scale below he
500 grams level, a medium touch certainly below 2000 grams, and you had
to press reasonably hard to get 5000 grams pressure.

If we start off with these very rough figures, and figure an "action
weight" of 100 grams on a the back of the key, then the soft zone is
going to pretty much be a pianisimo thing. Certainly by the time you hit
a blow of 500 grams we would be in the so called hard zone... no matter
which way you turn it if these assumptions are anything close to correct.

One other point I am a bit unclear on. The article seems to say that the
position of the breakpoint is independant of any key leverage ratio. The
location of the breakpoint is given as a = (r/rb)g. rk is given to denote
the distance from the fulcrum the <<action weight>> is applied to the
back of the key. In each case this yields then also the amount of input
force by the finger that is needed to achieve this breakpoint
accelleration... also independant of the keys actual leverage...??
Perhaps I misunderstand this ?

RicB




--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html
http://www.hf.uib.no/grieg/personer/cv_RB.html