Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.
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Inverse sidechain possible?
Sorry if this has been discussed before, but is there a way to invert the effect of a sidechain compressor, so it is ‘ducked’ with a low signal rather than a high one? Not the right words I’m sure but hopefully that makes sense 
I’ve done it before with FAC Envolver, using the resulting midi to automate a volume fader, but it’s a bit of a faff to setup.
I’m in AUM.
Comments
So, a gate?
EDIT: sorry, didn't read your question properly, you want to amplify one signal, inversely proportional to a control signal. I don't think any SC compressors or effects do this out of the box. You could do this in Drambo, if I understand correctly, you need your control signal to be converted to (0dB - its value), so it is "louder" when it's "softer", like a "complement" version. Then just sidechain this "complement" signal to a compressor with regular functioning.
Yes but using a sidechain source. Am I asking a dumb question?
Edit: looks like WoodnGate does this?
Yes, any expander (or noise gate), being the opposite of a compressor, will do (as long as it has a sidechain input, obviously 🙂)
Also, this is nearly an envelope follower
Yeah that’s what Envolver does. Well, it converts the envelope to midi.
Any other good options? I’ve been looking through the hundreds of apps I have already but Koshiba, perforater etc. don’t support side chain by the looks of it.
(fabfilter MB does it expand mode)
or i wrong you meant input sc signal itself
I’ve realised I can kinda get the effect I’m after using the envelope follower in Filterstation2. Last time I tried this was before multi out support in AUM.
I do realise it’s filtering rather than gating but it’s super simple to setup the sidechain.
For what it's worth, in general I prefer doing this kind of stuff using volume or filter cutoff automation. Far more versatile, uses less resources. People really only did it with sidechained compressors back in the day because it was easier to do with analog equipment.
(EDIT: of course that only applies if you have a simple sidechain signal, like a bassdrum etc...)
I know what you mean, but I’m specifically looking for the opposite: a pad or drone being ‘played’ by some or all of a drum pattern that’s definitely more complex than just a kick. I like the effect of this when it introduces the beat before the actual drums kick in.
I’m pretty sure it’s an envelope follower I’m after. Just looking for quicker/easier ways to do it than using Envolver and midi.
If you wanted to do a special multiband version of an envelope follower, you could use a vocoder (which is effectively a multiband arrangement of a group of envelope followers).
FAC Envolver can turn the envelope which can be thought of as a wave form outlining the inputs volume. The output of FAC Envolver can be a MIDI CC stream of values. So, FAC Envolver output can be mapped to the volume of any other channel in AUM.
So, a simple MIDI filter that inverts the "waveform" or basically subtracts the values of the FAC Envolver MIDI CC stream from some high value (like 127 or maybe a tad smaller) would
create inverse volume settings. So, as the input audio volume gets mapped to MIDi CC values (10, 20, 30) the MIDI is filtered to the inverse down from 127 to (117, 107, 97).
This is using MIDI conversion to "side chain" the envelope of one channel to control the
volume knob on one or mode other channels.
The MIDI filter would be trivial to code in Moziac or StreamByter. Just ask and someone will
provide the code but this assumes FAC Envolver is available. It's a powerful tool in the AUM toolkit for converting audio to MIDI patterns.
I'm sure there are tools in Drambo to build a similar audio to MIDI to volume mechanism.
I’ve always used FabFilters Pro-G for any side chain ducking / expansion duties. In Auria, on desktop and in AUv3 land. Edit: Ok I just realized that didn’t help the OP question...Edit2: Although you could control what is side chained based on frequency etc in Pro-G..hm
Yeah this is how I’ve done it before, mapping the midi to a volume fader or gain stage. It’s fine, I just thought there might be a more instant way now that multi out is a thing.
Thanks. I’m one of those annoying types that like my apps universal so I’m toneboosters rather than fabfilter. I’ll see if compressor or barricade have anything useful in them
You should be able to build it in NuRack (if you have it) using “velocity control” on one input to drive a gain module on another input in multi-input mode.
I don’t have nurack but this might be a good excuse to get it
Fabfilter Pro G
Woodngate!
Both already mentioned. Toneboosters apps also have started doing upwards compression since I created this thread.
Toneboosters Compressor has an “Audition” button.
Flux-Mini if you need midi.
https://apps.apple.com/us/app/flux-mini/id1548927370