When a four rank positif pipe organ was delivered unannounced to the shop of the local organ builder, he asked me to look after the electrical end of things. The organ, originally a tracker, had been unsuccessfully converted with electric pull downs. We removed these and used direct electric action instead. Fortunately the organ came with four of Roman Sowa's decoder/pipe drivers. I daisy chained these and assigned each rank to a different channel. Using a Midi controller with selectable channels we were able to test each rank.
But for voicing, we needed to be able to play ranks together and try the ranks at different pitch levels for some judicious unification. And although the owner intended to connect the positif to a larger pipe organ, I thought it would be nice if he could play the organ as a standalone right away by simply plugging in any old 61 key DIN Midi keyboard. I wanted to do this without building a stop rail, so I installed an Arduino based pipe organ "front end" inside the organ with a single Midi IN.
Those of you who are also faced with controlling a small pipe organ from a VPO console may find my solution to how I implemented the stop action interesting and useful.
Basically it involves giving up top C on the keyboard. Pressing that key causes a general cancel to occur and turns the top octave into stop selection mode. Up to 12 stops can be assigned to this top octave. Pressing these keys turns those stops on. (Shades of Hammond) When finished selecting stops one can simply start playing anywhere outside this octave which immediately causes the top octave (except for top C) to revert back to its normal playing function.
The code for this can be found on my website.
https://sites.google.com/site/casavantopus400/
If you study this, you will also see how I implemented the borrowing of the bottom octave from an eight foot step to extend a four foot stop. And while I was at it, when one runs out of pipes at the top, (possible with unification) I just "folded" those notes back an octave.
John
But for voicing, we needed to be able to play ranks together and try the ranks at different pitch levels for some judicious unification. And although the owner intended to connect the positif to a larger pipe organ, I thought it would be nice if he could play the organ as a standalone right away by simply plugging in any old 61 key DIN Midi keyboard. I wanted to do this without building a stop rail, so I installed an Arduino based pipe organ "front end" inside the organ with a single Midi IN.
Those of you who are also faced with controlling a small pipe organ from a VPO console may find my solution to how I implemented the stop action interesting and useful.
Basically it involves giving up top C on the keyboard. Pressing that key causes a general cancel to occur and turns the top octave into stop selection mode. Up to 12 stops can be assigned to this top octave. Pressing these keys turns those stops on. (Shades of Hammond) When finished selecting stops one can simply start playing anywhere outside this octave which immediately causes the top octave (except for top C) to revert back to its normal playing function.
The code for this can be found on my website.
https://sites.google.com/site/casavantopus400/
If you study this, you will also see how I implemented the borrowing of the bottom octave from an eight foot step to extend a four foot stop. And while I was at it, when one runs out of pipes at the top, (possible with unification) I just "folded" those notes back an octave.
John