[LAD] Open Keyboard: Request for velocity curve information

[David Olofson]

söndag 04 oktober 2009 19:43:38 skrev  Fons Adriaensen:
> On Sun, Oct 04, 2009 at 06:50:38PM +0200, David Olofson wrote:
> > Well, I don't know about linearity, or how linear MIDI velocity is
> > actually supposed to be, but it's common to at least have various ways of
> > scaling velocity. Many (most?) synths will support mapping of velocity
> > per voice to create "analog" layers (crossfade rather than switch at a
> > distinct velocity), and to exaggerate, reduce or disable velocity
> > response and things like that.
>
> The first question to ask is what is acually measured
> and how, and with which resolution.

Most likely the time elapsed from the first key switch is made to the second.

(IIRC from cleaning mine, the Fatars have the usual "bubbles" with conductive 
rubber switches; two per key. I also had some small Roland controller way 
back: Same design.)


> Then a range of these values must be mapped to 0..127,
> so the first thing to be decided is the limits of this
> range,

I suppose 0 would be somewhere around where a real piano would make no audible 
noise whatsoever, whereas 127 would be somewhere between where your fingers 
start hurting and where the hardware breaks. :-)

This would be the absolute limits *before* mapping. One would most likely want 
to map only a part of this range to MIDI velocity in the normal case. One just 
wants to avoid random zero velocities when playing very softly, as well as an 
obvious dynamic "brickwall" when playing real hard.


> next what kind of function maps it to the MIDI range.

The original Studiologic MCU has two integer parameters for this in the user 
interface; SHAPE [-4,4] and VELOCITY [1-8], where the former selects the 
mapping function and the latter scales the dynamic range of that function.

Unfortunately, I don't know how this is related to actual key velocities, and 
I'm quite sure one can't make it out from the instruction manual. ;-)


-- 
//David Olofson - Developer, Artist, Open Source Advocate

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