Super Aggro Mix Bus Compression for Metal

If you’re mixing modern metal, you know the struggle. You want that slammed, in-your-face mix bus compression that glues everything together and adds serious punch. But then, the double kicks turn into a mushy mess, and the low-end just chokes the life out of your track. What if there was a way to get that aggressive sum compression without destroying your low-end and transient detail? Enter the "Insides/Outsides" technique, a game-changer showcased by the legendary producer Machine (known for his work with Lamb of God and Suicide Silence) right here on Nail The Mix.

This isn't just another subtle tweak; it's a foundational approach to busing that can revolutionize how you get a massive bottom end and an exciting, dynamic mix. Let's break down how Machine uses this for bands like Suicide Silence.

The Classic Mix Bus Compression Problem in Metal

We all love what sum compression can do. It’s that secret sauce that makes a mix feel cohesive and powerful. But as Machine points out, metal, with its incredibly busy kick drum patterns and massive low-end energy, presents a unique challenge.

Here’s the deal: compressors react to the energy of the input signal.

• High Energy Triggers: Elements like kick drums, snares, and even chunky palm-muted guitars are spiky. They have quick, high-energy transients that hit your compressor’s threshold hard, causing it to react aggressively.
• Low-End Power: Bass frequencies inherently carry a ton of energy. Think about how much power big subwoofers need – it takes a lot of juice to move all that air!

When you’re mixing metal with fast double kicks or sustained sub-bass notes, these elements constantly bombard your mix bus compressor. The result? The compressor clamps down hard, stays down, and your guitars can get "wooed out" or disappear, losing all their punch and definition. The very tool meant to enhance your mix starts to ruin it.

This is a common frustration, especially if you love the sound of heavily compressed mixes from sparser genres but can’t get it to translate to metal. For more foundational knowledge on how compressors work, check out our guide to the basics of compression for metal.

Enter the "Insides/Outsides" Solution

Machine’s "Insides/Outsides" technique is all about getting the best of both worlds: extreme compression for character and vibe, plus clarity and punch where it matters most. The core idea is to split your entire mix into two main stereo buses before your final master bus:

• The "Insides" Bus: This is where the aggressive compression happens.
• The "Outsides" Bus: This bus typically has no compression, or at least much, much less, allowing critical elements to breathe.

Everything in your session – drums, bass, guitars, vocals, samples – gets routed to either the Insides bus or the Outsides bus. There's no escaping this highway; every track takes one of these two off-ramps.

Crafting the "Insides" Bus: Maximum Impact

The "Insides" bus is where Machine goes to town with compression. It's not just one compressor; he often employs a chain to get the desired effect. In the Suicide Silence example, he uses:

1. Subtle "Over Easy" Compression: The first compressor in the chain is described as a "beautiful silver compressor" (think something clean and smooth like an SSL-style bus compressor) set for a gentle, over-easy style of compression. It’s just starting to kiss the signal, not doing too much heavy lifting.
2. Aggressive "Supercharger" Compression: Next up is what Machine calls a "supercharger" compressor – something highly colored, dangerous, and capable of extreme squashing. He cranks this one, even adding saturation from the unit itself. This is where that "in your face," "dangerous," "fat," and "evil" character comes from.

The goal here is to get that exciting, pumping "dance" that heavily compressed mixes are known for. When the spiky elements hit, the compression ducks the sustained sounds (like guitars) momentarily, making them swell back up in the gaps. This creates a sense of loudness, presence, and energy, similar to what you can achieve with dedicated parallel compression on your drum bus.

The "Outsides" Bus: Preserving the Essentials

So, if the "Insides" bus is getting pummeled, what about those elements that were causing problems in the first place? That’s where the "Outsides" bus comes in.

This bus is your "get out of jail free" card for elements that would otherwise make your aggressive "Insides" compression fall apart. Typically, you’d send things like:

• Problematic Kick Drums: Especially fast double kick patterns that would floor the "Insides" compressor.
• Sub-Bass: The deep, sustained low-end of the bass guitar that carries immense energy.

By routing these to the "Outsides" bus, they bypass the heavy compression chain. This means their transients remain sharp, and their low-end energy doesn’t constantly trigger the "Insides" compressors into oblivion.

You have incredible flexibility here. You can send an entire track (like the sub-bass track) directly to the "Outsides" bus. Or, using sends, you can blend portions of a track to the "Outsides," giving you fine-tuned control over how much of that element escapes the heavy processing.

Insides/Outsides in Action: Machine's Suicide Silence Mix

Let’s see how Machine applies this. After getting a quick balance, he routes almost everything to the "Insides" bus (initially bus 31 in his example). The "Outsides" bus (bus 32) starts empty, except for one crucial element: the sub portion of the bass (a common technique you can learn more about in our guide to splitting your bass guitar).

Why the sub-bass first? Because that constant, powerful low-end would just hold the "Insides" compressors down, choking the mix. By moving it to the "Outsides," the "Insides" bus can dance and pump much more effectively.

But he doesn't just leave the sub-bass static on the "Outsides" bus. To make it groove with the rest of the heavily compressed material, Machine gets clever:

• Keying the Sub-Bass: He wants the sub-bass on the "Outsides" bus to still react to the kick. So, he inserts a compressor on the sub-bass track (or its bus if it’s split) and sidechains it to a “key spike” from the kick drum, a precise technique you can master by learning how to use MIDI key spikes to trigger drum gates. This "key spike" is a short, transient version of the kick, ensuring the compressor on the sub-bass reacts sharply and quickly.
• The Result: Every time the main kick drum hits, the sub-bass on the "Outsides" bus ducks down in volume momentarily, creating a pumping effect that syncs with the groove, even though it's not going through the main "Insides" compression chain.

He then experiments with moving the kick drums. If the double kicks are too much for the "Insides" bus, more of their signal can be routed to the "Outsides" bus to retain their attack and clarity. This creative routing ultimately helps solve the classic issue of low-end mud, a concept we dive deeper into in our guide on balancing the kick drum and bass in a metal mix. It’s a constant balancing act, creatively deciding what needs the aggressive "Insides" treatment and what needs the clean path of the "Outsides."

The "Dance" and Creative Control

Machine emphasizes the "dance" of compression – how it makes elements interact, creating space and perceived loudness. The "Insides/Outsides" technique allows you to achieve this desirable dance even in dense metal mixes. The "Insides" bus provides the aggressive character and movement, while the "Outsides" bus ensures crucial elements like kicks and sub-bass don't get lost or ruin the party.

This isn't a set-and-forget preset. It's a highly creative workflow that gives you immense control. You can:

• Move entire instruments between the "Insides" and "Outsides."
• Use sends to blend parts of an instrument's signal to the "Outsides" bus, retaining some of its character in the "Insides" while giving its problematic frequencies an escape route.
• Automate these sends throughout the song for different sections.

It’s about listening critically and deciding which elements are causing issues with your desired level of sum compression and then giving them a separate path.

Take Your Metal Mixes to the Next Level

Machine's "Insides/Outsides" technique is a powerful way to get those super exciting, massive-sounding metal mixes, but it’s just one way to approach your final bus; for another perspective, see how Dave Otero likes to set up a mix bus for metal. It's about being intentional with your routing and understanding how different elements interact with your compressors.

Want to see exactly how producers like Machine implement these techniques, dial in their compressors, and make every decision from start to finish on real-world metal tracks? At Nail The Mix, you get to watch world-class producers mix actual songs from bands like Lamb of God, Gojira, and Periphery, month after month. You get the multitracks and see every plugin, every setting, every move, from foundational routing to the final loudness decisions, like the difference between limiting vs. clipping for mastering.

If you're ready to go beyond presets and truly unlock your sound in modern metal, this is your chance to learn from the best in the business. Give the "Insides/Outsides" technique a shot on your next mix – you might be surprised at the power and clarity you can achieve!