Pretty simple with a midi processor :
Map any midi message with X value to :
Stop / Program Change X / Play
Without midi processor maybe any Program change followed by Note 35/B1 (sequencer restart) is enough. Didn’t try.
Do you have midi processors (hardware / software) or other advanced midi things?
If the master needs to start playback at some other point (as set by a Song Position Pointer message), then a MIDI CONTINUE message is sent instead of MIDI Start. Like a MIDI Start, the MIDI Continue is immediately followed by a MIDI Clock “downbeat” in order to start playback then.
http://midi.teragonaudio.com/tech/midispec/seq.htm
I don’t have a kenton or the likes. But I’m thinking about getting one.
Check this. Don’t hesitate to tell what are your needs, in order to help to choose one.
Midi Processors with Octatrack
OT manual
MASTER SCALE sets the general time signature of the pattern. This setting is completely independent of the individual track tempo multiplier settings. It is used to define the overall time signature of the pattern, which affects MIDI clock if sent out by the Octatrack. When an Octatrack arrangement is being controlled from an external MIDI device,the song pointer position will be affected as well.
So…YES! IT WORKS! 
:
I can play any step of the Arranger, on the fly.
I mapped midi notes (Note number X, Velo Y) to
Stop (FC)
SPP (F2 X Y)
Continue (FB)
I tried midi loopback, but it freezed. 
. I’ll try to understand why later.
BAR 1 - F2 00 00
BAR 2 - F2 10 00
BAR 3 - F2 20 00
BAR 4 - F2 30 00
BAR 5 - F2 40 00
BAR 6 - F2 50 00
BAR 7 - F2 60 00
BAR 8 - F2 70 00
BAR 9 - F2 00 01
BAR 9 / step 2 - F2 01 01
BAR 9 / step 3 - F2 02 01
…
BAR 9 / step 16 - F2 0F 01
Game changer yes : MULTI MAP for OCTATRACK!
It means that with midi notes, it’s possible to change patterns, pattern repeat / offset / length, scenes, bpm, mutes, and transpose all midi tracks on the fly.
Game changer indeed!
So 8 years later new stuff is being discovered… that is an exceptional achievement
EDIT so now I have a new RK-002 project 
As OT can send SPP per row*, it would be interesting to make a midi learn mode with RK002 : Play a note, send the SPP after to associate notes and rows.
*Transport send On, choose row + enter, out of Arranger edit mode.
SPP take account of Arranger Repeat, Length, but not Offset.
If you add a loop row, it seems to add loop length, if infinite, or loop length multiplied buy the number of repeats.
Great to hear that it works.
Well, since these are no MIDI channel messages which can be easily “terminated” within the OT I guess a loopback will let these messages loop forever.
And what should the machine do when it receives and endless stream of STOP/CONTINUE/STOP/CONTINUE … ?
If it is possible to reprogram your midi processor to filter out STOP/CONTINUE/SPP when it receives them, then a loopback should work.
I planned to check midi thru with a midi monitor to see what is the buggy message.
Yes. OT was supposed to receive Transport only.
Possible with the RK002
The SPP message is like this
F2 LSB MSB
1 LSB = 1 step, 1 MSB = 128 steps
I think the easiest is to make correspond a row to a note value, mapped to MSB, so each row has to be 128 steps. Even for short pattern, it is doable with arranger Repeat, Length, Loop.
Might not work for original pattern lengths.
In that case, to play a specific step I’d rather use arranger Offset rather than LSB.
Just had a crazy idea : if another message, mapped to LSB, is incremented at each step, theorically I think you can do direct jump (change pattern and play starting from the step corresponding to the previous pattern).
Can’t wait to try!
Finger crossed.
It’s true that using a RK002 as a midiloop cable it’s almost like if we had a customizable firmware. Given that the RK002 is an Arduino platform with most of the Arduino IDE implemented everything Midi can be manipulated in endless ways. Speaking about Midi Real Time messages: clock can be maniputated (warped… ) too! Imagine setting a LFO to modulate the tempo…
I think I can do that already with EPP+, mapping midi ticks to an arp and modulate it’s speed.
RK002 can go very far, for sure…
And yes it works!
OT midi loopback, randomization of rows with random notes on step 5 and 13, direct jump.
Same pattern with 4 different scenes.
Thanks for luring me into this thread, @sezare56.
I have a fairly extensive midi controller, however under song position/song select there is only the mention of No. Beats… no parameter to enter the likes of your (F2 X Y) And I couldn’t get anything to happen.
One would expect song control would be a staple function on a pedal, why does it have to be such a pain in the abyss, i don’t know.
Also I can’t say I understand this at all :
I mapped midi notes (Note number X, Velo Y) to
Stop (FC)
SPP (F2 X Y)
Continue (FB)
Could you explain how you are managed to jump around the arranger in your video, please?
I don’t remember precisely, but I was sending midi notes with an OT midi track as timing reference. The midi processor converting notes to a SPP message, sent when receiving a note on another channel.
Not simple!
The SPP message is like this
F2 LSB MSB
1 LSB = 1 step, 1 MSB = 128 steps
I think the easiest is to make correspond a row to a note value, mapped to MSB, so each row has to be 128 steps. Even for short pattern, it is doable with arranger Repeat, Length, Loop.
In that case, to play a specific step I’d rather use arranger Offset rather than LSB.
