Sidechain SC3 issues

I’m having a few issues getting sidechain compression, specifically using SC3, working on OS X.

I tried a while ago with Ardour 2.7.1, and have recently tried again with 2.8.12 ($0 version, planning to pay after this issue is solved) and haven’t had any luck with either.

Essentially, what I’m trying to do (in this instance) is ducking a piano track under a vocal track. I have looked on this site and others, and have set up a bus with SC3 (as well as a bypassed SC1, but that didn’t help) and sends and inserts from the vocal and piano buses. I have tried almost every permutation of input channel for the key and varied the SC3 parameters to no avail.

The problem essentially is that SC3 seems to be ignoring the key input (and not really compressing at all, though I can’t be 100% sure). The outputs also seem to be mono - the levels are the same for left/right, when the input levels are very different.

This is happening on OS X 10.6.8 Snow Leopard, with swh plugins 0.4.15 (the ones that come with Ardour 2.8.12). I haven’t gotten a chance to try this project on a linux box, but I’d like to be able to do it all on the Mac. Any ideas?

Also, somewhat unrelatedly, I would appreciate it if anyone could point me to instructions on compiling LADSPA/LV2 plugins on OS X.


Compiling most LADSPA and LV2 plugins on OS X requires some work coding, typically at least modifying the build system, ir not the code itself.

And in as far as SC3, short version is it doesn’t seem to be working correctly.


It might be a bug in the OSX compile of SC3 but have a look at my answers #5 and #8 on to see if you’re doing things wrong.

@peder - I configured things exactly like you specified (actually several times, but I just re-tried it) and it still didn’t work.

Looking at the input monitoring, things are coming in (all 3 signals) just fine.

Switching to pre-fader metering (SC3 applied pre-fader), the dB meter for channels 1 and 2 don’t move - completely silent - while the channel 3 one does not exhibit any compression.

@seablade - Good to know about SC3 not working correctly.

Any suggestions for other sidechain compressors that might work on OS X?

Alternately, I don’t really have a problem compiling myself, but I don’t really know where to begin - or rather, how to compile a single plugin. I downloaded the SWH LADSPA plugin sources, and ./configure told me I needed FFTW. Again, I’m not opposed to installing it, but I would eventually like to write my own plugins and being able to compile them individually would probably be a good thing. I’ll keep playing around with things, but any links to info on compiling LADSPA on OS X would be helpful.

TL;DR: Any other sidechain compressors that work on OS X?

Thanks for the quick response!


It isn’t working, I tested it before I posted as I was making a video to show how to set it up even.



Well my goto is Mixbus’s mixbus compressors which all have sidechains. Now whether that is an acceptable solution to you or not, I can’t answer.


Having taken a look at Mixbus, it seems like it will do what I need. The only problem is essentially a moral one - I have access to ProTools 9, but I wanted to transition away to an open source solution. Transferring to Mixbus is less closed-source, but transferring from one closed source app to one that’s less closed defeats the purpose of moving at all.

I think for now I’ll manually automate it, but if anyone else has suggestions for getting a sidechain compressor working in Ardour I’d love to hear about it.

Nah you have the right idea most likely, you just need to find a working sidechain plugin for it. Sad to say I don’t have any solutions for you in that regards.

What I will pass along is that the only part of Mixbus that is closed source is the DSP itself, the codebase for everything else is in Ardour’s SVN and in fact many of the recent fixes etc. for Ardour 2.x came directly from the development that took place for Mixbus. Whether this changes your opinion of it or not is up to you of course though, I understand some people still don’t like anything closed source.