[sdiy] Make a CS80

[Tom Wiltshire]

On 5 Apr 2010, at 12:09, cheater cheater wrote:

> On Mon, Apr 5, 2010 at 12:50, Tom Wiltshire <tom at electricdruid.net>  
> wrote:
>>
>> 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,
>
> tactile feedback
>
>> or a high-pressure switch at the
>> maximum pressure.
>
> more tactile feedback
>
>> Both 'switches' can be implemented as thresholds on the
>> output from the pressure sensor.
>
> This won't be as repeatable on the electronic side because of
> variations in the parts;

This is a common enough problem with pressure sensors and even mod/ 
pitch wheels. Most systems have some sort of calibration routine to  
deal with this. The Rhodes Chroma is one example from way back.

> but more importantly it won't be repeatable
> on the human side - because a human can't really learn muscle memory
> based on a threshold somewhere in 'mid air'. Ever tried to learn how
> far up from the ground is exactly 1 meter?

This is a poor analogy. We're not 'in mid air'. You'll feel when the  
key touches the pressure sensor (it's the end of the travel) which  
gives you tactile feedback for that threshold at least. You might not  
feel when the sensor reaches maximum, but you *can* learn how hard  
you're pressing, so you'll get your muscle memory.


>>> 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!
>
> Which would be just fine, because you can always make a converter :)

Great! Now every bit of kit I own is like a Roland Juno with a DCB  
interface hanging off the back of it...except that there's no  
standard for it to convert *into*, so I either have to come up with  
one of my own, or build a convertor to deal with all the combinations.
I realise you're joking, but this is a nightmare!

>>
>> 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
>
> Who cares about end-users? :-)
>
> And seriously, we're talking about pro equipment here. If a synth
> could cost 10000 usd of today-money, then what difference did it
> really make if you needed a converter that cost 800? None for someone
> who looked at this as an investment.

If it costs 10000usd, I'd want it to wake me up with a cup of tea in  
the morning! For that kind of money, being able to talk to other  
devices is essential - without any convertors or kludges.

>> (How many different IR remote controls do you have in
>> your lounge?! Why didn't *they* find a standard to work to?)
>
> Or, you can have an universal remote, which existed since the 80s!

Exactly. People have been forced to buy a third-party kludge to fix a  
problem that didn't need to be there in the first place.

<snip>
> MIDI really is that rubber pear, it robs the user of any possibility
> expression; anyone who's ever played a real musical instrument knows
> that velocity is just a tiny factor in the overall sound.

Umm, a piano? That's a real instrument, and a pretty successful and  
well-thought-of one. The mechanism *only* allows you to control  
velocity, since after the key is struck, the hammer flies free until  
it hits the string. Any amount of key-massaging is pointless,  
although it might make you look like a virtuoso.

Expression based on velocity alone *is* possible, but it isn't like  
that's all MIDI gives you. Aren't you forgetting about the aftertouch  
that we started out with (either mono or polyphonic), the wheels, the  
foot controllers, breath controllers, pedals, etc, etc - and that's  
just the obvious ones that MIDI designers thought of. Of course you  
can use parameter changes to inject even more tweaks. MIDI doesn't  
limit your expression a great deal, at least not compared to a  
Bechstein, and no-one's complaining about those.

T.