In this first installment in a
two-part series, we’ll take a
look at compression as it applies
specifically to us guitarists. For
starters, we’ll talk about using
compression in the studio and
how you can apply it to your
tracks during mixdown. Next
month, we’ll examine the differences
between compression
pedals you’d typically use in the
recording process and plug-ins
or hardware you’d use after
you’ve finished tracking.
Briefly, compression is about
controlling the dynamic range
of your instrument. A compressor
reduces your volume using
a set of controls that vary with
each type of device.
With your typical studio-based
hardware unit or
software plug-in, the main
controls are
Threshold and
Ratio. When audio peaks rise
above your chosen Threshold
setting, they are reduced.
Anything under the Threshold
setting is not reduced or
affected. Ratio determines
the amount of gain reduction
that happens after the audio
rises above the Threshold setting.
For example, a typical
3:1 Ratio setting means that,
if the audio rises 3 dB above
the Threshold setting, the
compressor will hold that level
to only 1 dB above the threshold,
thus reducing the peak by
2 dB. Very high compression
ratios yield an effect called
limiting, which we’ll explore
in further columns.
The other set of adjustable
controls found in most compressors
are
Attack,
Release,
and
Makeup Gain. Attack
determines how fast or slow
the actual compression takes
place, and Release governs
how quickly it lets go of your
signal. Makeup Gain lets
you raise the overall output
level after you’ve compressed
the audio, thus maintaining
a robust signal even though
you’ve reduced its peaks.
With electric guitar, compression
is not always necessary—especially when mixing
heavily distorted parts. For
example, when recording with
distorted tube amps, you’ve
already got a lot of compression
built into the sound (courtesy
of the power tubes), and compressing
the signal further in
the mix may make it mushy or
washy. In that situation, I may
compress very lightly—perhaps
using a 2:1 or 3:1 ratio—and
then apply makeup gain to add
some volume. Even that may
not be required: My old Gibson
amps sound compressed right
at the speaker, so I tend not to
compress guitar parts recorded
on them.
But with lightly distorted,
clean, or acoustic parts, I compress
a bit higher (4:1 or so)
and again use makeup gain.
In that case, I just want the
compression to barely hit, so
that only a few peaks that stick
out are reduced. Sometimes, I’ll
choose not to use compression
at all and just let the sound ebb
and flow naturally. Or, I use
volume automation to bring
down specific spikes in a part.
Different makes and models
of compressors have unique
tonal qualities. For example,
the Waves API 2500 plug-in
sounds quite different from
the Sonnox Oxford plug-in.
Both are compressors/limiters,
but each has its own different
character. So don’t think that
just one compressor should
be applied and that’s that.
Try different types and see
what works. I think of the
Waves compressor as having
“color,” because it includes
tone-shaping options (as does
the API hardware version).
So I’ll turn to that when I
want to control the texture of
a particular instrument, such
as a distorted electric guitar.
But with compressors like the
Sonnox Oxford (which models
a mixing console that costs
six figures), I think of them
as “non-colored” or “transparent.”
I tend to turn to those
when I want to maintain clarity
on acoustic guitar parts or
clean electrics.
Sometimes I’ll put a
compressor on and set the
Threshold so it barely peaks
at all, using it simply as a gain
processor. You can do that
by turning up the Output
Gain (most compressors feature
this control). Of course,
you can raise levels using a
Volume fader, but the difference
is that if a part jumps
up suddenly, the compressor
will grab it and hold the level
down. The fader alone will
not do that.
Note that over-compressing
a part will squash the dynamic
life out of it and make it sound
dull. However, I do sometimes
record a distant room mic when
cutting guitar parts and then
intentionally over-compress
it during mixdown for effect
(especially using the Universal
Audio 1176). Panning the over-compressed
room sound hard
left or right can deliver a wide,
ambient guitar tone.
There is no right or wrong
way to apply compression.
Whatever sounds right, is right.
Again, each type of compressor
has its own sonic thumbprint
and the only way to know what
it will do to your guitar part is
to apply it and listen.
Rich Tozzoli is a
Grammy-nominated
engineer and mixer who
has worked with artists
ranging from Al Di
Meola to David Bowie.
A life-long guitarist, he’s
also the author of
Pro Tools Surround
Sound Mixing and composes for the
likes of Fox NFL, Discovery Channel,
Nickelodeon, and HBO.