# Compression of stems via sidechain from summed master.



## chrisr (Jan 11, 2017)

Hi All,

I'm intrigued to know if any of you are working in this way and how you find it.

I compose in Cubase and track stems to Reaper (slaved) to produce draft mixes and then ultimately stems (14-ish) for the full mix session (done elsewhere)

I often think that the underscore suffers from a slight lack of compression, particularly evident when dialogue and sfx are brought back in to the mix.

For my current movie project I thought I'd try setting up so that I could apply some gentle, low level, parallel compression on all the stems, such that they'd sum just as if the parallel compression were applied on the music summing bus, to effectively raise level of the softer moments and low level details.


The stems channels are all controlled via VCA (so that I can ride the whole music mix) and then summed, before being mixed with the dialogue and sfx. I wanted to achieve a compressed sound _pre-fade_ so that I can still gently ride the underscore via VCA, but retain the balance of the stems with _each other_.

To do this I sent each stem to the summing bus (& on to master out). I also sent each stem to a duplicate dummy bus, pre fader.

The sum of this dummy bus feeds the side-chain of compressors on each stem track. I have some moderate/firm compression dialled into each stem, mixed back in parallel to the dry signal, such that the quiet moments are subtly raised in volume whilst the louder bits are not perceptibly altered.

As the compression attenuation is from a summed master the balance of the stems with _each other_ is unaffected, but the summed stems have a pleasing, very gently compressed quality which is sitting in the mix very nicely for me.

I'm really delighted with the results. I'm sure others have had similar thoughts before - so is anyone else working this way?

best,
Chris


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## Tysmall (Jan 11, 2017)

Thanks for sharing, that's a really interesting idea.
Though subtlety would be key, I am curious as to what ratios you are using, and are you going to automate the ratios manually throughout the piece?
I feel like using a single knee and and ratio throughout could sound too noticeable and out of place at some parts - Say you have a loud dialogue part, at a low ratio you can only duck so much gain and it might compete for space.
I am also pondering the idea of a sidechain eq going with say Neutron for example. You could duck 3k at quiet scenes and really let the voice shine through.


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## chrisr (Jan 11, 2017)

The compression itself is at a low ratio (1.3:1) with a moderately slow attack and release and a very soft knee. The threshhold is set so that in very quiet passages it's not compressing at all, at medium levels it's compressing 3-5db and in very loud passages it's around 10db (!). However, as it's in parrallel (unity dry, very low mix of wet - internally mixed in the plug in) the resulting effect is that in loud passages the summed sound isn't noticably changed, whilst in very quiet passages the volume of everything is increased a little.

I won't change these settings throughout the whole movie, but alongside this (mild) process I can manually mix levels via the vca, which alters levels after the compression. Ultimately it'll be mixed by someone else , but my stems will all now have a slightly reduced dynamic range, and will sit at about the right place in the mix against the dialogue.

I'm hoping that this will just help some of the finer details cut through a bit more easily when it's mixed, certainly it's helping me with my temp mixes. ABing the compressed and uncompressed versions shows pretty subtle but nice differences, just as if I had put a small bit of parrallel compression on the main music bus, but of course doing that would throw out the balance of the stems to each other when bouncing them out, which is the whole point of doing it this way instead.


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## Fab (Jan 12, 2017)

It sounds like something interesting but ts kind of difficult for me to understand what your saying you did. Do you have time to do a short example video on it?

It sounds similar in concept to this video below, is that not too far off?



thanks,

Fab


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## chrisr (Jan 13, 2017)

Hi Fab,

Yes, what I did was very much like that video but just with a different, less aggressive style of compression as I'm composing underscore. That video was made some time ago, so it looks like I'm somewhat behind the curve on this technique.

In Reaper the same result is achievable in a different way, but it's basically the same technique - just aimed at mimicking what would happen if I put a compressor on the master music bus.

Now I've done it once, I think I'll be doing this whenever I deliver stems in future.

I'm afraid I don't have time to post a video example because I'm up against deadlines, sorry!

best,
Chris


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## sinkd (Jan 13, 2017)

Try this:

Bounce a mix of all the stems without any two bus compression. This will later be your "trigger track" but it has to be at the final levels, volume automation, etc.

Then mix everything into your two bus compression and get all of the settings finalized. When you bounce the individual stems, send the "trigger track" to the sidechain input of the two bus compressor. The compression on the individual stems will be responding to the full, pre-compression "trigger" and not just to the material on the stem.

The only caveat is that the sidechain input will be mono only.


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## chrisr (Jan 13, 2017)

sinkd said:


> Try this:
> 
> .



Well, that's the spirit of what I've done, except that in my case the sidechain is stereo, and also the way I've set-up I don't have to print a dry mix 'trigger track' - it's all happening in realtime (exactly like on the video clip above I think - although I only scanned quickly through it I'm afraid...)


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## sinkd (Jan 14, 2017)

Cool. @chrlsr: What compressor plugin do you use?


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## chrisr (Jan 14, 2017)

It's the stock Reaper compressor Reacomp, it's rather well featured... image attached....


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## chrisr (Jan 14, 2017)

That's just an image i found on google btw.... not my settings  am not in the studio... but where it says 'detector input' you can select another stereo key input.


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## Joram (Jan 16, 2017)

chrisr said:


> Hi All,
> 
> I'm intrigued to know if any of you are working in this way and how you find it.


I am familiar with the idea and Ithink it is a clever way to setup a mix. However, as a mix engineer I like to have more hands-on control and I think it is smarter to gain ride your tracks and stems. In my opinion this gives more natural results and more room for musical dynamic control and this makes it easier to bring the mix to the next level.

bwt I work with different stem tracks with a.o compression plugins that have a parallel ratio control. I do not have anything on the master bus.


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## chrisr (Jan 17, 2017)

Hi Joram,

I agree that riding levels is the way to go initially. I should say that all of that mixing/balancing of levels happens in my Cubase session, as I'm composing, so that I'm printing "mixed" stems to Reaper. I then just want to preserve the balance of levels of the stems in reaper (with the odd exception).

Invariably some cues end up relatively louder than others after the initial composing stage as I get a bit excited during the writing... so I use clip gain to bring the cues to about the right level in reaper, before using a VCA fader to ride the levels of the music as a whole when needed. I don't do anything terribly drastic with the VCA as the whole thing will be mixed elsewhere eventually.

So my mixing process (from this job on) is:

1. Levels mixed in Cubase (as ever) as composing, to get good natural balance.

2. Stems printed to Reaper for each cue.

3. Clip gain on all stems (equally) to get to right ball park against rest of film/dialogue/other cues.

4. Distributed light compression of stems using the technique in original post, such that overall loud levels remain about the same and quiet levels are raised just a little bit so that they don't get lost.

5. "VCA" (well, not really...) of all stems from a master track to nudge any particularly unruly bits back into line.

6. Bounce stems from this reaper session to stereo bwavs for delivery to mix.

Although I'll only ever do it that way when I have to deliver stems - otherwise it's open season on the stereo buss, as usual 

My natural instinct is to not want to piss off the mixing engineer by trying to do his job for him - I had just shy of 20 years in audio-post in the UK before I started writing full-time so I have sat on the other side of that table! I have a good relationship with the chaps who will mix this movie. It's an animated film so they have a gargantuan track count of dialogue and sfx - there is zero live/production sound - everything in the environment is individually track-laid and panned/moved around the sound stage in somewhat painstaking detail, along with a voice cast of maybe 15 voice actors. The mix sessions (this is my second of these movies) are far bigger than anything I ever mixed in my time behind a console (which was mostly TV, radio and corporates) - so my hope is that what I give them this time will mean that they have to do as little work as possible to get my cues sitting well in the mix - goodness know they have about a million and one things to think about.

There'll be a viewing mix/playback session in March, so if my posts suddenly stop after that it means they didn't like what I did...

Forgive me, what are "a.o compression plugins" (googled but couldn't figure it out) ??

best,
Chris


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## Joram (Jan 17, 2017)

Hi Chris,
That explains a lot. It seems you have some experience mixing  Nice project as well. Interesting to know how you setup the music session and the final post session.

Do I understand it correctly that you are meaning you are kind of mastering the stems? Which is indeed a good idea especially when working on music for television. 

Since you are mixing the whole show, why wouldn't you compress the stems in final post session? How are you anticipating on the final session when mixing the music?



chrisr said:


> My natural instinct is to not want to piss off the mixing engineer by trying to do his job for him


hahaha. Never piss off the mixing engineer 



chrisr said:


> Forgive me, what are "a.o compression plugins" (googled but couldn't figure it out) ??


On my stem busses are different plugins "among others compression plugins [....] Depending on what I like and what's needed for the track that could be a multiband compressor as well, some kind of tape emulation thing and an ms-processor.


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## chrisr (Jan 17, 2017)

ah, "among others" ... I see 

Do I understand it correctly that you are meaning you are kind of mastering the stems?

I wouldn't say I'm mastering the stems so much as just gently giving them a teensy bit of compression. There's still a lot that can be done at the final mix.

I'm often doing rough mixes to get cues approved. My rough mixes are all delivered in stereo and I whack a further compressor on both the master music bus and the maser mix bus (containing dialogue and a few temp sfx that are added by the animation studio) - so that it's a quick and dirty balance but reasonably full sound for the producer and director to sit and listen to.

When I'm composing I often have the dialogue and (temp) sfx _very_ low, to protect my sanity and to focus on the music. It _may be_ that having them so low is encouraging me to write too quietly or subtly in some passages - and that the stem compression I'm applying later on is really just unf'ing something that I wouldn't have f'd in the first place if I'd been monitoring all the elements in a better overall balance whilst I was writing. As I say, I'm pretty happy with what I'm hearing at the moment so I'll carry on like this for the foreseeable...

How are you anticipating on the final session when mixing the music?

Well of course the line between composition and mixing is incredibly blurred and it's hard to say where one starts and the other ends, but I have to deliver cues that I _guess_ will work against the pictures and other audio as best I can using previz animations (and occasionally animatic) and having temp dialogue and sfx tracks with all sorts of things in there that won't be in the final mix. So it's all a bit of educated guesswork really. (edit * - oh and temps of course!)

I've long been used to the idea that _many_ things can change creatively after I've delivered the music - so in terms of anticipating what the final session will end up like... well, I may find that whole cues have been chopped/rearranged/removed and otherwise altered by the producer/director. So I just do the best that I can and trust them.

On the previous film in this series there was a hard cut that I hit with a metaphorical sledge hammer. It was changed to a long cross fade for the final render (!)... no point in losing too much sleep over it I guess. I dare say not too many people thought it was too unusual in the end (apart from some musician friends who I'd explained it to before we went to see the movie...)

why wouldn't you compress the stems in final post session?

There will be further compression and maybe other processes on the music bus when the full mix is put together I'm sure - but that's not my call. What I'm describing here is simply that I'm getting what I deliver to them into a very slightly better place than it was before.


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