MIDI on ADC organ

[John Vanderlee]

Ok, we're into playing around with our 2nd ADC4500. This one has an Allen MIDI circuit on it, but no tab! However, someone heavily modified a lot of stuff, and we're trying to bring it back to a 4500 factory spec. What exactly would this MIDI box be capable of? It's mounted under the key desk.

[toodles]

Allen's ADC MIDI provided for note on and off only for each of 4 divisions, in this case pedal, accomp, great, and solo. The box underneath the keydesk would only have connectors for the MIDI--or it might also have audio inputs if it is Allen. Perhaps this is a 3rd party system, in which case you'll need to identify who made it and contact them for details.

The Allen MIDI adapter has an input connector for MIDI On and Off for each division; the control can be tabs, a rotary switch, toggle switches, or whatever. For some owners, they might leave MIDI on all the time and control the sounds on/off on the MIDI sound generator.

[AllenAnalog]

The Allen MIDI translator card connects in the data stream between the console multiplexer board and the card cage on ADC organs. They also made an optional box with cables to remote the MIDI connections to the front of the organ, rather than having to open the back of the console to access them. You may also have headphone connections in the box up front, depending on who made it.

As noted by Toodles, the Allen MIDI card has multiple inputs on a separate connector to turn the MIDI OUTPUT of each division on and off. (The MIDI INPUT always works. Whenever there is valid note-on and note-off MIDI data on the channels used by the organ it will play the organ notes.)

The MIDI Out is controlled by grounding the terminals on the MIDI control connector (marked P572). In my case, when I added the MIDI board I only wanted to use one tab to control the MIDI Out of my 3 divisions so all three wires are connected together to the same REM output on the console multiplexer board. If you don't need to turn MIDI Out on and off at the console you can just permanently connect all of the MIDI control terminals to ground.

If you need more specific information about the MIDI output channel control connector wiring, one of us with an ADC MIDI board installed can help with that.

[John Vanderlee]

Ok Got it! Now if MIDI is always on , either with the all the divisions on with a single tab or on separately, how does that affect the MIDI device it outputs to?

I mean, would the device play from all divisions, or with separate on off controls could you select the division it plays from? I can't see the point of the device playing from all keyboards simultaneously.

[AllenAnalog]

To be super clear about this, the MIDI Out data stream has the same channel number assignments for the divisions of the organ as the MIDI In. Even if you turn all divisions of MIDI Out on and off with one switch, each note-on, note-off message will have a MIDI channel number associated with it that is dependent on which keyboard you are using to play those notes.

The synth or sound engine you send the MIDI Out signal to from the organ totally determines what happens to that information. In that device you have to associate each channel number with a particular voice or group of voices. That is usually called the "patch" - a term harkening back to the days of wired patch panels.

[toodles]

Many MIDI sound generators allow you to assign a different voice to different MIDI channels, or no voice at all. Sometimes MIDI can be set to receive in an OMNI mode, so it reacts to messages on any MIDI channel.

An advanced MIDI sound engine can offer a lot of control on its own, including, perhaps, some preset selections by channel. So whether or not you need the Allen to control which channels (divisions) are on and off depends upon what you are connecting it to and how flexible that device is.

If you want to control which divisions on the Allen are sending MIDI data, you need to add some switches to turn on and off the MIDI divisions. The Allen adapter allows for individual selection for each of 4 divisions. Four small toggle switches would suffice, and they could be hidden discretely alongside the ARTE unit or, perhaps, nicely tucked under the stop rail without be an obvious "add on".

[jbird604]

It's a nice touch IF you have the spare tabs, to give each division a MIDI stop of its own. This way, the external sound engine can be set up beforehand with whatever patches you intend to use. Then you can reach up and flip the tab on and the MIDI voice will turn on just like any other organ stop, and turn off like a regular stop when the tab is canceled. This makes the external MIDI voices function much like the Allen "Alterable" voices, with the advantage that you can set up different patches for each division of the organ. (As described above -- the external MIDI device itself should allow you to assign different voices to each different MIDI "channel" number, and these "channel" numbers correspond to the different keyboards of the organ.)

On the large cage ADC Allens, you must have spare "REM" outputs to which the color-coded MIDI channel control wires are connected. With the MADC models you can simply connect the color-coded wires to separate unused tabs anywhere on the rail.