The Octatrack is excellent for hardware MIDI modulation, maybe the best, but if you are looking for a very simple box it might not be it. That said, the complication of the octatrack stems primarily from its breadth of function. So if you ignore the audio side completely and consider it only as a mega MIDI modulator/controller it becomes much easier to grasp. This might seem extravagant but mk1 prices have come down quite a bit and just the MIDI half offers a lot of unique features.
It has 8 tracks of midi sequencing with independent midi channels, and each track has 10 customizable midi cc’s plus pitchbend and aftertouch. These 12 parameters (along with note settings, arp settings, and LFO settings) can all be modulated with any of the track’s 3 LFOs. These can run freely and asynchronously but where it gets interesting is how the LFOs interact with the sequencer. In elektron speak LFO is a catch all for both traditional LFOs and envelopes, so trigger sequences can be used to fire off envelopes or reset LFOs. These triggers can have logic conditions applied to them to create complex generative patterns. Furthermore, besides some bread and butter LFO/envelope shapes there is an “LFO Designer” for each track where you can create extremely compex LFO shapes/patterns with steps and smooth slides with curvature controls - almost like a mini sequencer. Finally if things get a little too wild you can use “parts” to immediately return to a prior point or move forward with a completely different preset of everything mentioned above.
There are downsides however. The most glaring for me was the total inability to label the cc parameters which means sticking to a template and doing some memorization. Even a 3 letter abbreviation would have done wonders in this regard. The other issue is the relatively sparse physical user interface compared to what’s going on under the hood - there’s really only 6 encoders available to be manipulated at one time. The parameters for the LFOs and CCs for the 8 tracks are spread across 24 different selectable pages so you have a narrow funnel through which you interact, though switching pages is only one or two button press away.
The few physical controls and lack of labeling can be easily solved, albeit in an unwieldy way, with one or more knobby MIDI controllers. So theoretically you can have every parameter on the octatrack broken out as a labeled, physical control, which would just be a ridiculously powerful MIDI modulator. For people fond of desktop/keyboard instruments it would be glorious, but most will simply move to a software or CV modular environment to get their modulation fix.