It works with 2 midi tracks that send CC94 to the same channel (one DN track).
On the first track you have CC 94 = 0, on the other CC>0
Then you mute/unmute these OT midi tracks accordingly
I hoped I could control 4 DN and 4 A4 tracks from the OT arranger
Possible with a midi processor : OT sends CCs when you mute / unmute from Mixer page, or regular mutes. Easy to map a midi track mute to CC94 0/1.
Well, one more sign that tells me to buy a midi processor
And that way you can also send any message from OT midi track. 
You can even use that track to control another synth one a different channel (remapped).
Ok I tried with a midi monitor. OT is definitely weird but in that case it can be useful :
You can toggle between CC94=0 and CC94=1 with one track. But you need a second track.
Mute / unmute track 1, it will toggle between CC94=0 and CC94=1 instantly, if track 2 is unmuted.
I noticed that weird behavior before. T1 has priority over T2 when it has the same CC. The most surprising thing is that the T2 CC is queued, and sent as soon as you mute you mute T1 !
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Im looking for a octatrack and this will be brillinant if it can be done in one chanel only.
It might be possible if in one track the first step mutes and the last (with microtiming) unmute. This way when the track is active is always mute, and when you desctivate it it always unmute becoue of the last step of the previus pattern.
Can anyone try?