[sdiy] Make a CS80

[Tom Wiltshire]

On 5 Apr 2010, at 11:00, cheater cheater wrote:

> I think that it would be nice to have both a proximity/position sensor
> (hall?) for reading how far the key is depressed, and a pressure
> sensor at the end of the travel, followed by a final high-pressure
> tactile switch that presses in when the pressure sensor is at the
> maximum.. that could make for some interesting playing techniques
>
> For example you could control a pan flute sound, and the position
> sensor could fade in more 'breath' as you're depressing the key. Once
> the key touches the pressure sensor (which could have a metallic
> terminal with a matching terminal on the key body to tell when the key
> is there) the resonance could start happening and the pressure would
> control the crossfade between the breathy sound (making it decay to
> 30% at maximum pressure) and the resonance (making it raise to 100%).
> Then the tactile switch would completely decay the breathy sound to 0,
> via a 15ms release time.

You've got some good ideas, but you don't half make things complicated.
If you've got a pressure sensor already, what's the need for contacts  
to detect whether the key is touching it, or a high-pressure switch  
at the maximum pressure. Both 'switches' can be implemented as  
thresholds on the output from the pressure sensor. A zero reading is  
"key not touching", <5units is "key just touching", and >95units is  
"maximum pressure".

> Or you could have a violin style sound where the string gets bowed
> when you're depressing the key, then the pressure heightens the
> vibrato, and the tact key plucks it and the sound is over; this could
> be used by quick-handed players to have control between
> bowing/staccato/pizzicato.
>
> This scheme doesn't even exclude the additional information of
> velocity, but definitely gives it a new context, and it could be used
> for something else yet to give even more expression to the sound..
>
> Had only MIDI not happened, we'd have hundreds of synths like that
> since the 80s.

And they'd all use some proprietary protocol and none of them would  
talk to any of the others - great!

I realise you have a deep-seated hatred of MIDI, and I agree it is  
getting a bit long in the tooth, but it did a great job. Standard  
wars are an absolute PITA for end-users (How many different IR remote  
controls do you have in your lounge?! Why didn't *they* find a  
standard to work to?) MIDI meant that you could buy a keyboard from  
any manufacturer and be sure that it would talk to equipment made by  
*any* other manufacturer. It made the whole computer-music bedroom  
studio thing possible, and opened up a whole world of options. There  
are many things it doesn't do, and it is a bit keyboard-centric, but  
it was an incredible effort given the time it was done.
Anyway, speed was always MIDI's biggest weakness, and with MIDI-over- 
USB, that's becoming a moot point. It may yet live into the 21st  
century.

T.