[sdiy] MIDI volume to volts formula

[chris]

I don't even think the actual transfer function is really important. 

So you could use exp, inverted log, square (normalized to 0..1), gamma
(as in graphics), or even a quarter circle (ok, may degenerate due to
infinite derivative) - as long as 0 maps to 0 and 127 maps to 127
(wouldn't be necessary, but seems to be common). 
Add some spicy coefficients or combinations of the above to create a
couple of variations, so the user can select from a handful of options.

I think it's just about somehow bending the linear transfer
funnction towards harder or softer without introducing any steps.

Maybe even the big companies don't put much emphasis on this, I remember
the DX7 keyboard only generating velocity values up to 100. DX patches
really come to life when played from a piano action master keyboard...

Chris



On Thu, 7 Jun 2018 17:43:01 +1000 Adam Inglis <21pointy at tpg.com.au>
wrote:

> 
> > On 7 Jun 2018, at 5:02 PM, rsdio at audiobanshee.com wrote:
> > 
> > 
> > On Jun 6, 2018, at 6:07 PM, Adam Inglis <21pointy at tpg.com.au> wrote:
> >> On 7 Jun 2018, at 4:48 AM, Ben Bradley <ben.pi.bradley at gmail.com> wrote:
> >>> On the other hand, I think a piano is a roughly linear function of
> >>> input velocity (or force) and "signal" output. This may require
> >>> "original research."
> >> 
> >> There must be a stack of research out there, possibly some of it in-house/proprietary by the big instrument makers, regarding this.
> >> I would’ve thought you be better served by a sinusoidal function, rather than log or linear, but of course it is going to depend mostly on the qualities of the particular tone or patch you are controlling at any one time (even more than personal playing style).
> > 
> > Why sinusoidal? Are you suggesting the volume should eventually decrease and then go negative as velocity increases?
> > 
> 
> Aaah, sorry, that should be sigmoidal, not sinusoidal!! Duh.
> 
> As in this 
> https://en.wikipedia.org/wiki/Sigmoid_function
> 
> These sorts of shapes are very useful when tailoring velocity to “playability” on a per patch basis.
> 
> 
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