[LAU] So what's the deal with controlling the aeolus organ stops via midi

[Fons Adriaensen]

On Sun, Oct 04, 2009 at 03:33:46PM +0200, Dominic Sacré wrote:

> Unfortunately it's not that simple. Most hardware MIDI controllers will 
> let you send continuous controller values or toggle between two values. 
> But to control the stops in Aeolus you basically need to be able to 
> manipulate individual bits of the controller values...
> 
> Some time ago I wrote a small script that might be just what you need. 
> It uses mididings (http://das.nasophon.de/mididings/) to convert normal 
> MIDI controllers (one CC for each stop) to Aeolus' CC 98. You'd just 
> need to insert it between your MIDI controller and Aeolus.

The basic problem here is that MIDI doesn't have anything
close to what is required. On a pipe organ you can switch
each stop on/off independently of all others. MIDI is not
designed to do that, its 'preset' model is something quite
different. The standard Aeolus setup has around 55 stop
buttons, and that amounts to more than 2^55 ~ 3e16 =
30000000000000000 combinations or 'presets'.

The easiest way to control Aeolus from MIDI is to create
a number of presets in Aeolus (it can have up to 1024)
and then use the standard MIDI messages (bank/preset) to
select one of them.  

If you really want to control individual stops that is still
possible using normal controllers. You need (for the standard
instrument) 4 buttons to select one of the four groups, and
16 buttons to select a stop within a group. If you organise
things this way then each button just needs to send a single
controller message.

The essential thing to understand is that switching a stop
on/off is a two-step process. First you select a group and
and action (on/off/toggle), then you select a stop within
that group. The first (group/action) message is stored, you
only need to send it when it changes. This is really no more
complicated than the concept of preset banks.

Apart from all this, mididings is the perfect tool to
manipulate all things midi. Using it you can map Aeolus'
control messages to whatever you want. 


Ciao,

-- 
FA

Io lo dico sempre: l'Italia è troppo stretta e lunga.