Hi, and welcome back.
I made a video recently about Waves R Bass, and I threw together some example music for
the purpose.
While mixing that music I found myself reaching for two parallel filter techniques, which
I thought I would show you.
I'm not talking about the parallel distortion for the bass: it's two other techniques I
have in mind, both of which, I'm afraid, will be slightly more awkward to set up if you're
not a Reaper user.
And in so doing I'm hoping to highlight that these are techniques I genuinely use for mixing
or sound design, I'm not just trying to come up with weird audio engineering trick shots
for my channel!
So let's start with a synth part, from Arturia Pigments; this is an awesome synth by the
way, which I'm hoping to find the time to learn properly one day; but extensively glitched
out using Automaton from Audio Damage, an old favourite of mine which is now free I
believe, in case you haven't grabbed it yet.
Ok.
Now I also have a guitar part, playing the same chords, and also glitched out with Automaton.
I guess I was in a glitchy mood that day.
Awesome.
Except, when I put them both in together…
it gets a bit too much.
It's overwhelming and confusing.
Ok, let's start by routing the synth part to a parallel channel, with no processing
at all… it gets 6dB louder.
No problem, I'll drop the fader to compensate, and as it's a post fader send I don't need
to touch the parallel channel.
Ok, now another send from the guitar channel… but this time I'm going to flip the polarity
for just this specific aux send… and the guitar disappears: it nulls.
This is the Reaper specific part: most DAWs don't allow you to flip the polarity for a
send; it seems like a small thing, but it's really useful!
Anyway, now we have a parallel channel that's simultaneously boosting the level of the synth
channel, while nulling out the guitar to silence.
And if I flip the polarity of that parallel channel, they swap over: now the synth cancels
out and the guitar is boosted 6dB; let's compensate the guitar level too.
This is already a kind of interesting setup: we could automate the polarity for this channel
to create an AB switching setup and rapidly glitch between the two parts…
But that's not what I have in mind.
You know what they say: if you love it then you gotta put a filter on it.
Can you guess what kind of filter though?
I'm going to answer that question with a visit to the Plugin Doctor, and another parallel
setup in Metaplugin.
This time I've got Volcano 3 running in parallel, and I've loaded an all-pass filter.
In case you don't know, an all-pass filter passes all frequencies and has a totally flat
frequency response, but will just shift the phase instead.
A 2 pole all-pass like this rotates the phase by 180 degrees at the target frequency, with
the phase shift trending back to zero either side.
I'm using the Clean filter style, so this is just a standard digital all-pass filter
with none of the saturation special sauce.
When I add this phase shifted signal to the original, the stuff that's 180 degrees phase
shifted cancels out, so we get a notch filter.
And if I flip the polarity for just the filtered signal…
it turns into a bandpass filter.
Can you see where I'm going with this yet?
Let's go back to our example mix, and add an all-pass filter to that parallel channel;
I'll use ReaEQ, just because… and now we have a notch filter for the synth, and simultaneously
a bandpass filter for the guitar at the same frequency.
Or I could flip the polarity and get a notch for the guitar and a bandpass for the synth…
and of course I can adjust the width of both filters simultaneously… and sweep the frequency
around… or automate it, or modulate it.
I confess that actually I used Volcano 3 for the all-pass filtering in the R Bass video,
because I like the FabFilter modulation options, but I could have got much the same result
with this stock plugin.
Ok, that's a pretty cool trick, right?
But it leans more to the sound design side of things: its not a transparent way to fit
two parts together in a mix, like the actually very similar Super Separator trick I showed
you a while back.
So I'm going to follow it up with a mixing trick that I've found really useful.
Here's the scenario: you've been playing around with bass fattening tricks like those we looked
at in the R Bass video, and you've found a bass sound you're happy with.
But then you step back and take in the bigger picture, and realise that you've lost the
low end of the snare drum.
The snare doesn't actually sound that thin if the drums are solo'ed however… and I'm
pretty sure it didn't sound thin in the mix until I fattened up that bass sound.
So clearly there's a masking problem here.
But I like what I did to the bass part and I don't want to undo it, so I'm going to try
to fix the masking problem with EQ instead.
And you probably know how that goes: you'll need a combination of some boost for the low
fundamental of the snare, which with a real drum recording might mean boosting those frequencies
in the close mics and the overheads and maybe the room mics too… plus a cut in those frequencies
on the bass part, and probably keys and guitar as well.
If you're working smarter with more of a top down approach you may be able to simplify
this by boosting one EQ on the drum bus, while cutting on a subgroup or two containing conflicting
parts of the mix.
But you still have to balance a boost against a corresponding cut: tweaking two parameters
simultaneously is one area where mixing in the box puts you at a disadvantage, because
your mouse only does one at a time.
Wouldn't it be nice if you could adjust one parameter which dialed in the boost and the
cut at the same time?
Well, hold my gin and tonic: parallel channel again, and we'll have a bandpass filter this
time, and create a send from the drum bus.
I'll tune the filter to the drum's low fundamental, much as I did in my parallel bandpass filters
video… but I'm not going to make it quite as tight and narrow as I don't want audible
ringing in this case.
And now we've got a 6dB boost for the snare drum fundamental: probably too much, the mix
is getting a bit tubby, but we haven't finished yet.
Next we create a send from the bass subgroup, which includes the parallel distortion channel
I set up in the R Bass video, so this is the whole bass sound that I'm sending… and now
that's also boosted at the same frequency, which is exactly the opposite of what we want.
No problem: I'll flip the polarity for just the send again… and that boost turns into
a notch filter… which is way too extreme of course, so I'll usually turn the send down
a few dB as well.
And I'll do the same for any other subgroups with content that might mask the snare: in
this case just this one Everything Else group.
Great: now I can adjust the fader on the return channel to dial in my cut and boost at the
same time: here's the original balance… and notice how the snare fundamental comes
out through the mix as I wind this back in… that's pretty amazing, right?
We can take it further however: I'm going to add a downwards expander after the filter
on the parallel channel…
I'll keep the ratio quite low and gentle, but set the threshold so the signal never
quite reaches it, and rides the expansion all the time.
I've also got a pretty fast attack and some lookahead so I can catch all the transients.
Now we've got expansion for the low fundamental of the snare drum, boosting it harder whenever
it hits… and we also simultaneously have compression at that frequency for the rest
of the mix, ducking that region down harder whenever the snare hits.
But importantly, those two processes now also interact with one another: when there's a
lot going on in that region of the mix the level feeding the expander will increase,
meaning more boost for the snare and more cut for everything else…
and vice versa, when that region of the mix isn't getting cluttered up, the expander will
back off on the parallel channel, and both the boost and the cut will relax together.
Let's have a listen to the difference once again…
Final point: the channel name.
I call it delta, meaning difference, and if there's a bandpass filter on it I'll include
the frequency its tuned to.
Maybe you can think of a better name?
Let me know in the comments.
Thanks for watching.