FluidSynth Output is Hopping Around Channels L and R


since yesterday, out of nowhere, I have the strangest problem:

I’m using the setup described in this post:

After booting up the Zynthían and loading the snapshot, E-Piano and Grandpiano are on channels R and L respectively, but for the first 2 minutes or so are jumping around channels like crazy.

I play on the keys and every 4th note or so the sound is hopping to the other channel. Then, 2 minutes later and after opening MOD-GUI it stops doing that and seems to work normal.

Anyone encountered this, also? Possible remedies?

I’ll be blunt, as long as it takes only a couple of minutes to “settle down” - I don’ really care, but it is a strange beaviour nonetheless.


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After using it live, I can say the FOH will not be amused by that behaviour…

Could you upload the sound recording from the zynth of this issue? That eill at least confirm the jackd side of the process. . .

It 's really strange. Could you confirm that your Power Supply is a good one? As you probably know, inadequate power supplies are the first cause of strange problems …

Hi I’m aware of that PSU issue. I’m using a 3A PSU, which should be more than enough, I guess. Will do some recordings/video in the evening.


Turns out I am not able to consistently reproduce this behaviour. Now it works fine most of the time. Only occasionaly it happens.

Does i happen with a particular soundfont? I have observed the salamander piano has samples with different stereo position for some notes based on the velocity which makes it unusable.

The stereo swapping is exactly the first thing I heard when playing a grand piano sound in the rehearsal room. It’s a little subtle coming from a PA but I heard it. The soundfont I used was handcrafted, so the problem lies not within salamander…

Then I made a setup where epiano is on one channel and grand piano on the other. There you could hear the swapping clearly.

But as I said, as of now I can’t reliably reproduce it. I have more trouble with the snapshot not taking on the soundfonts I intended.

I know what you mean. It seems to be such a little thing but playing it live that way is indeed impossible.


I’ve been using Zynthian for 3 rehearsals now, and everything went just fine! Well after one or two reboots.