Support and discussion for all of Akai’s modern standalone MPCs including the MPC X / X SE, MPC Live 1, 2 & 3, MPC One / One+, MPC Key 37/61.
By jamos Thu May 29, 2025 12:18 am
Can anyone point me to coherent, preferably written (as opposed to video) explanation of how modulation works in the OPX-4?

This instrument is glorious, but the mod matrix is unlike anything I have ever seen, and not necessarily in a good way. In every other synth I have ever used, modulation is added to the initial value of the destination; but in the OPX-4, it seems that the initial value is multiplied by each mod routing. Also entirely unclear are what the types (Unipolar, etc.] mean in this context. And what the difference is between Velocity1 and Velocity2. Etc.

It really is nice that they have the animated bars that show the modulator and the final effect on the destination, and I suppose I can puzzle it out that way, but an actual explanation would speed things up.
By jamos Thu May 29, 2025 6:46 am
B-Wise wrote:Here's the OPx-4 manual: https://www.airmusictech.com/user-guides/opx-4.pdf

I know you wanted written help, but this was the best 7 video series I've seen on OPx-4:
https://youtube.com/playlist?list=PLoxH ... kNQAEtFZbo


Thanks. I have of course read the manual, it's shockingly scant in this and and every other regard. I'm aware of that video series, I checked out his topics and he doesn't mention modulation at least not as a top-level topic, I'm doubtful that he'll address it in any detail but I will try to find the time to watch it. Video training usually takes an awful lot of time to get a very little bit of information, but if that's what there is, that's what there is.
By B-Wise Thu May 29, 2025 8:34 am
jamos wrote:
B-Wise wrote:Here's the OPx-4 manual: https://www.airmusictech.com/user-guides/opx-4.pdf

I know you wanted written help, but this was the best 7 video series I've seen on OPx-4:
https://youtube.com/playlist?list=PLoxH ... kNQAEtFZbo


Thanks. I have of course read the manual, it's shockingly scant in this and and every other regard. I'm aware of that video series, I checked out his topics and he doesn't mention modulation at least not as a top-level topic, I'm doubtful that he'll address it in any detail but I will try to find the time to watch it. Video training usually takes an awful lot of time to get a very little bit of information, but if that's what there is, that's what there is.


Some here made a thread going into some deeper stuff on OPx. I don't remember if it covered what you want. Also I watch most videos with the time playing faster. Press Shift and > on YT a few times or put in a custom play speed.

Here's the link if this doesn't cover what you want Ask the who made this post for help:
viewtopic.php?f=48&t=217622&hilit=opx+4
By Masi Thu May 29, 2025 7:24 pm
jamos wrote: Also entirely unclear are what the types (Unipolar, etc.] mean in this context.

Unipolar means IMHO the same as it does for other synths. The modulation goes from 0 to max as opposed to -max to +max for bipolar.

jamos wrote:And what the difference is between Velocity1 and Velocity2.

Velocity 1 and two are the same: the velocity of the note. The idea is that you can use different scaling for each of them (eg linear for 1 and logarithmic for 2).

And yes, the manual sucks and the videos only scratch the surface. With experimantation I could figure out bits, but when I tried to put it down in words (even only notes for myself), I failed.