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[timg11]

I have an HD1 program that seems to have an unknown LFO modulating the filter.

I have OSC2 turned off, and am working with OSC1 only.
Filter 1 is in 4-pole mode.

All filter modulation sources (EG, LFO, Keyboard track, ribbon, aftertouch, are set to zero.

Yet there is a low-speed LFO (one cycle every 5 seconds) sweeping the filter across its full range! It sounds like a triangle or sine modulation.

I raised the speed of all the LFOs - OSC1, OSC2 and common LFO just to see if one was the source, but none of affect the speed of this slow modulation.

What other sources could modulate the filter frequency like this? There must be some "sneak path" I'm not seeing.
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Kronos2 73, Presonus StudioLive, Cakewalk / Sonar Platinum, Windows 10

[timg11]

The plot thickens...

I thought I would upload a PCG containing the program that exhibits this strange behavior. The program was using one of my user samples, so I changed it to a ROM sample.

With the ROM sample, the strange modulation is gone.

With my user sample, I had previously bypassed the filter which caused the modulation to also disappear, so I know it wasn't in the sample.

However, now when I go back to my original user sample, the modulation is also not there.

This all started when I was looking at a setlist, and saw "Samples not loaded". I checked the underlying combi, and found the program with the problem.
I opened the program and the sample bank was set to "Smp: Old RAM Stereo", and the sample was set to "00032".
This is an old program, and it has been set to a user bank for a long time, so I have no idea why it has developed this problem spontaneously. When I made the sample change above, I had saved this out to a new location, so I had the original program. I started the process over with the program that was showing Samples Not Loaded.

I set it back to the proper user sample bank and sample, and went back to editing the filter. The same slow LFO sweep is back.

I've already spent hours, so I'm going to stop and just chalk it up as an unexplained occurrence. If anyone has insights, or wants to look at the program, let me know.
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Kronos2 73, Presonus StudioLive, Cakewalk / Sonar Platinum, Windows 10

[Liviou2004]

Are you sure you have bypassed all effects, too ?

The Unison parameter creates a modulation, depends on settings. This is not a filter modulation but a pitch modulation. Are you sure you heard a filter modulation and not a pitch one ?