Hi, any idea how this could be achievable?
I believe this is not possible within the elektron sequencer, maybe with some midi processor?
up 
set your device to recieve clock and send it from a daw, most of them can change clock on the fly and have it as a mod destination.
for hardware solution maybe theres some modular gear that can do that?
ive only used the digi so i dont know if octa can naturally do it within the box.
but if you want to have like a tempo riser on a digi, song mode is pretty good for that.
dividing your patterns into 2 step mini patterns, each of which increase tempo a little, placing them all in a row, ect. 
I found a max4live device called paradox that can modulate live’s tempo
https://maxforlive.com/library/device/8520/paradox
this is also possible in Ableton to use the LFO to modulate the Arpegiator rate set to “free” mode.
I’d love to achieve that with hardware though…
do you mean tempo sync?
The toraiz Squid does that too, in the manual there is an explanation on how it’s “speed modulation” shapes can alter a pattern’s trigger timing
Thanks, I’ll try to explore song mode
edit : I tried on the analog four. as the tempo is linked to a pattern, I looks reaaaaaly tedious to do, as you have to copy and edit multiple occurence of the same pattern, and then insert them each into the song.
I quickly checked the new song mode in the DIGIs, it seems many parameters including tempo and pattern length can be edited per row, sounds an easier way to achieve tempo modulation inside a pattern. I’ll try and report!
