Adding chorus on a mono track

I have a mono track (guitar recording) and I want to add chorus effect (Calf multi-chorus). The chorus plugin has stereo inputs and outputs. What is the correct way to connect such a plugin? I can easily connect the (mono) input to both inputs of the plugin, but what to do with the outputs?

Good question, I am in my learning curve too so I tried this, maybe it can help. Create a test new project and added a mono track, recorded my voice and looped, I can hear it thru L and R. Go to Window > Audio Connections, the audio connections window will appear. Click on Ardour tracks tab for sources and destinations, you can see that your mono track has one single input but has L/R outputs.

I then added the Calf Muti Chorus (before the fader) and noticed the panning controls changed for stereo (before this it was a mono panning control) and even when the stereo panning is centered I can hear my chorused voice on L speaker only. Right click on Calf Muti Chorus plugin on the plugin area and selected “Pin Connections”, I can see a single green pin at the top of outer rectangle (the single mono input) and two green at the top of the inner rectangle (the stereo inputs of the plugin?), there ins only a single connection so I added a second input connection link and now I can hear both L and R.

Aren’t there any mono-input, stereo output chorus plugins?

As for stereo-chrous, it depends on the plugin, but in many cases you can send same mono input to Left/Right inputs and use stereo-out (compare to the flexible i/o schema below)

That should not happen. Which version of Ardour is that? Can you try with another (not calf) stereo plugin on a mono track and please report a bug if you can reproduce this?

With strict I/O: the track is supposed to Remain Mono (no panner change) and when adding a stereo-plugin only the plugin’s left input and left output pins are connected.

With flexible I/O: adding/removing a plugin can change the channel configuration. Ardour will adjust and the track will indeed become stereo (panner changes). Also both outputs of the plugin will be connected.


Of course you can always manually customize this, but by default Ardour should not change the output port count nor the panner when you use strict-i/o (except for instruments MIDI -> Audio see ). and with flexible-i/o ardour should connect all the pins, without any manual intervention.

I wanted to reply that I didn’t see the panner change, but as Robin mentions this should indeed not happen.
I can configure the plugin manually to have an additional audio out ‘pin’, connect this to the DSP and then the track becomes stereo in all aspects.
With flexible IO setting, the chorus pluging automatically changes the track to stereo.

Since Calf plugins are generally frowned upon, are there good (preferrably free) alternatives for Chorus?

Guitarix has some, and CAPS C*-chorus sounds nice.

Airwindows has a big pack of plugins (cross platform). There’s a chorus in there too.

Thanks for the pointer. Unfortunately “cross platform” seems to mean Mac + Windows. Not Linux.

There’s definitely a Linux bundle. I use it myself.

I must have overlooked that link. Thanks!

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FWIW, I really like GVST’s GTriChorus on guitars.

Sounds nice, thanks!