[sdiy] Aftertouch via Pressure

[harrybissell]

If you are willing to hinge the entire keyboard.... then optical, and resistive
methods
are easy as well.

iirc (but it has been a long, long time) the ARP ProSoloist had aftertouch from
a mechanically
pivoting keyboard...  otoh that one I saw was the FIRST time I saw any
synthesizer in the flesh... along with the Odyssey and 2600 models.  (high
school demonstration)

H^) harry

Glen wrote:

> At 05:39 AM 7/9/03 , jhaible at debitel.net wrote:
>
> >But the mechanical part is difficult. You must find a way to insert
> >the tube (hose?) beneath the keys, such that it's equally actuated from
> >blacks's and white's. And, worst of all, you have to find a way to
> >get enough key travel even with the additional thickness of the
> >tube. But then again, the SH-2000's keyboard also has reduced
> >key travel, and it plays nicely ...
>
> Mount the back edge of your keyboard assembly on a hinge, possibly piano
> hinge (that eliminates any alignment problems of multiple small hinges.)
> Place the front edge of your keyboard assembly over the sensor hose (which
> would run from left to right, underneath the whole keyboard.) The front
> edge would need some springs added to help hold the keyboard assembly down,
> just in case your instrument was ever turned upside down--possibly when
> being transported. You might even add some "return" springs underneath the
> front edge of the keyboard to ensure that the keyboard would move back up
> to its proper resting position after you stop pressing down on it. The
> rubber hose underneath the front edge will provide a spring effect of its
> own, but this will probably need to be augmented with such actual springs.
> Using return springs also allows you to use a more flexible and more
> sensitive type of tubing underneath the keyboard assembly. This should give
> you a more sensitive assembly that needn't be pressed so hard that you
> think you are going to break something, just to get some after touch. (My
> Kawai K4 has after touch, but is far too stiff and insensitive for my
> taste. I feel like I'm going to break something just trying to activate the
> after touch.) If you mount your whole keyboard on a hinged sheet of stiff
> metal (sort of a sub-chassis), you could even move the tubing away from the
> front edge of the keyboard. This would allow for adding more pressure to
> the hose, for a given amount of applied downward pressure, at the expense
> of having to press the keyboard farther, due to leverage effects. (I hope
> you know what I mean by this.)
>
> All of this assumes that you only want to develop a global pressure
> parameter, and not have individual after touch sensors underneath each key.
> If that's what you really want, it's going to get a lot more complicated.
>
> I look forward to hearing from other Synth-DIY members, as I haven't
> actually seen a keyboard built like I'm describing, but I think it should
> work. Let me know what you think. The advantage of my technique is that it
> does not screw around with your keyboard's key action--just the keyboard
> assembly mounting. The keyboard's keys should play with the same "feel"
> that they always have.
>
> later,
> Glen Berry