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Parallel compression

Gazillion Industries ·

Somebody hands you a record where the drums are obviously squashed and obviously still snapping, and you spend a week trying to get both out of one compressor. You cannot. There are two copies of those drums on that record.

Parallel compression means blending a heavily compressed copy of a signal underneath the untouched original. The dry copy keeps the transients, the crushed copy raises everything quiet enough to be missed, and the fader between them sets how much weight you want. Set the compressed copy to a high ratio, a fast attack and 10 to 20 dB of gain reduction, then bring it up under the dry track until the drums get heavier without getting duller.

The short version

What
a crushed copy blended under the dry one
Ratio
8:1 to 20:1, or the highest the compressor has
Attack
fast, so the copy has no transient left
Amount
10–20 dB of gain reduction on the copy
Blend
start at silence, raise until it thickens, then back off
Watch
latency between the two paths, and mud below 100 Hz

Why the blend works when one compressor does not

A compressor on its own can only trade. Push it hard and the quiet detail comes up, but the transient goes with it, because the same gain cell handles both. Two paths let you keep the spike on one and lose it on the other, which is why the technique got its reputation on drums, where the spike is the whole point.

The crushed copy behaves less like a second drum kit and more like the room the kit is in. Sticks, ring, breath, the tail of a sampled break, the hum of the record it came off: all of it arrives at roughly the same level as the hits, which is exactly what a room does to your ears at volume.

How to set up parallel compression

  1. Send the drums to a new bus, or duplicate the track and mute the output of one copy.
  2. Put a compressor on the copy, ratio 8:1 or higher, attack fast, release medium.
  3. Lower the threshold until the meter shows 10 to 20 dB of gain reduction.
  4. Solo the copy: it should sound flat, loud and slightly unpleasant.
  5. Pull the copy's fader to silence, unsolo, then raise it until the drums get heavier.
  6. Stop as soon as the transients start to soften, and take a dB back off.
  7. High-pass the copy around 80 to 120 Hz if the low end is turning to soup.

If your compressor has a mix or dry/wet control, it does the same job in one instance, and it sidesteps the alignment problem below. Some people call that parallel compression too, and arguing about the name has never improved anybody's drums.

The alignment problem

Two paths only stay a blend if they stay in time. Any plugin that reports latency will be compensated by the host, but a plugin that adds delay without reporting it, or a lookahead setting you forgot about, smears the two copies against each other and thins the result. The symptom is a blend that sounds worse as you raise it rather than louder, and often a hollow ring around the low mids.

Check it by inverting the polarity of the compressed copy with the compressor bypassed: the two should cancel to near silence. If they do not, the paths are not aligned, and no amount of fader is going to fix it.

DRUGS has MIX on the face with zero latency anywhere in the path, so the dry signal stays sample-aligned with the wet one and parallel compression does not comb-filter at any setting. It is free.

Where it costs you

Parallel compression raises the average level of everything it touches, which means noise, bleed and the low hum under a sampled break come up with the drums. On a clean modern kit that can sound like someone left a preamp on. Kick and 808 territory gets crowded too, because the blended copy fills the gaps the kick was using; high-passing the copy or ducking it against the kick gives that space back. See how to mix kick and 808 if the low end is the part that stopped working.

It is also easy to overdo on a whole mix. Weight on a drum bus reads as power; weight on the master reads as fatigue by the second chorus.

Questions people ask

What is the purpose of parallel compression?

To raise the quiet parts of a sound without flattening the loud ones. You get the density of heavy compression and the transients of no compression at the same time, set by one fader.

How do I do parallel compression?

Send the track to a second bus, compress that bus hard with a fast attack and 10 to 20 dB of gain reduction, then blend it in under the original until the sound gets heavier. Or use the mix control on a compressor that has one, which does the same thing in a single instance.

What is the best compressor for parallel compression?

One you can push into 15 dB of gain reduction without it turning to mush, with a release that recovers between hits. The crushed copy is meant to sound wrong on its own, so transparency matters less here than on the main bus.

Is parallel compression the same as New York compression?

Yes. New York compression is the same blend under a different name, usually with very heavy gain reduction on drums.

What DRUGS does

DRUGS is our free one-knob bus compressor for drums. DOSE moves the transfer curve, the knee, the attack and the release together, the way a single hardware macro would, and makes a drum bus denser rather than louder: peak level barely moves across the whole range of the knob. MIX is the dry/wet, with zero latency anywhere in the path, so the dry signal stays sample-aligned with the wet one. Auto-makeup is applied after the gain cell, so setting level cannot disturb the dynamics.

Two copies of the drums, one fader. That record you wore out was never doing anything else.

Keep reading

DRUGS — a one-knob bus compressor for drums, free for Mac and Windows. One control called DOSE, with GAIN and a soft ceiling on the way out.

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Gazillion Industries LLC · reading material