[sdiy] MIDI CC with Pots

[Paul Maddox]

Welcome to the world of synth design :)

the short version (I'll start with that) is that there is no right or 
wrong way to do things.
Do what feels 'natural'.
I will caveat this, no matter what you do, some people will hate it, and 
some will love it.

> -= PROBLEM 1: MIDI CC and Pots =-
>
> The synth has several pots for adjusting various controls of the sound
> (knob per function). The controls will also respond to MIDI CC. There
> can be a conflict in how the synth responds to both messages.
>
> OPTION 1: I recommended having the synth use whatever message it last
> received, whether a pot change or a CC message. This provides
> flexibility in usage and allows the use of both MIDI CC and the pots
> at the same time. This is how most of my synths seem to work.
this is how, to the best of my knowledge, every other synth I've come 
across works.
I know very few people who use MIDI CC at the same time as turning a knob.
usually the MIDI CC is used in a DAW to get a particular effect, for 
example haveing a bass line running and using MIDI CC 74 to open the 
filter cut off slowly over say 2 bars.

I don't think the second option is a great idea sorry, limiting the way 
a musician works can be incredibly frustrating for them. when a musician 
is in a creative moment you want to do everything you can as a designer 
to help them capture and enhance that moment, not hinder it.
Having a flick a switch back and fourth to enable MIDI or front panel 
control is going to really frustrate some people.

> -= PROBLEM 2: Mod Wheel =-
>
> First, he had a control that could only be changed by the mod wheel.
I had that on the Monowave, but that was because I ran out of panel space :)

> The synth has no built-in mod wheel (MIDI control only) so I explained
> how some synths have a joystick style pitch/mod control. On these
> synths, the mod level is always reset to 0, so it would not be a good
> idea to use it as a dedicate control.
not always, a lot of joysticks can have one spring removed, so you could 
have a centered action for left and right (say pitch bend) and a non 
centering action for up and down (say LFO depth and filter cut off).

>
> OPTION 1: I pointed out that the mod wheel is usually used for
> modulating an existing control that has its own value already. It adds
> more LFO to the oscillators or opens the filter more than the current
> cutoff setting. It is not usually a dedicated control on its own. This
> means that it only adds to the current value of a control that is set
> with a pot on the synth. Since he agreed to add an extra pot for the
> thing that the mod wheel will control, this is very easy to employ and
> won't slow the synth down much (just add the mod CC to the current pot
> value and limit it to the max value of the control). This also means
> the pot for the control will have its own dedicated CC for setting the
> base level, and the mod CC will only add to that.
sounds like a great idea to me.
>
> OPTION 2: He wants to add a switch to change the way that the synth
> handles the mod CC. This will allow the control to be disabled for
> anyone who is using a joystick style pitch/mod controller. This limits
> the usage of the synth for some people (anyone using it with a
> joystick).
again, really think about anything that 'limits usage' and how it can 
impede someone when they're 'in the moment'
>
> OPTION 3: He also talked about the possibility of not using the
> modulation CC at all. I own many synths, and all of them that have
> MIDI respond to the mod wheel CC. I think that this would be a bad
> idea because musicians expect the mod wheel to do something.
totally agree, it's not difficult to add and gives you a far more 
expressive instrument than without.

I'm well aware there's always a trade off when adding features;
more features = great powerful synth
more features = more drain on resources like processing MIDI, etc

but it is important to remember you're building something that is to be 
played as an instrument.
It's very easy as an engineer to add something, or do something that you 
think is the kippers knickers, only to discover musicians will look at 
you like you're from an alien planet and say "WTF were you thinking man?"

Find yourself a musician friend who plays keys, not a technical guy.
Talk him through the options, don't go into detail and see how he feels.

Paul
--
http://www.modulus.me