AI Metal

The Low End Is a Zoning Problem

Kick, bass, and rhythm guitar all want the same 60–120Hz range, and in an AI-generated track none of them arrive pre-negotiated for space. High-pass the rhythm guitars at 80–100Hz — not lower, or the low-mid content that makes a chug feel physical goes with it; not higher, or the riff thins into a buzzsaw. Guitars were never meant to carry sub-80Hz information. The bass and kick own that register, and stacking three sources there doesn't add weight — it cancels and smears.

Bass takes the 60–100Hz fundamental plus a narrow lift around 700Hz–1kHz for pick attack, so it still reads as a note when the guitars drop out for a breakdown. Kick splits into two non-adjacent jobs: sub weight at 50–70Hz that's felt more than heard, and click at 2–4kHz that lets the beater register through a wall of downtuned distortion. Scoop the kick between 300–500Hz, where it holds no useful information and only adds boxiness — sub and click then do more work at lower overall level than any midrange boost could manage.

Meshuggah's tone is a useful reference point here — tight and chest-felt without fighting the kick for space, because the parts occupy different registers rather than doubling on top of each other. Drop C, Drop A, and 7-string B-standard push those fundamentals into different places, which is why the tuning needs to be known before these cuts get set, not guessed.

More Gain Reads as Less Heavy

Distortion gain and clarity move in opposite directions past a point most AI models default to. Every stage of clipping adds harmonic content, and once several distorted guitar tracks stack, that harmonic buildup collects in the 300–500Hz band — not the frequency anyone associates with heaviness, but the one that decides whether a riff sounds like a riff or a wash of static. Pulling 2–3dB out of that range with a wide bell, on each guitar track individually before they're summed, recovers more perceived weight than any amount of low-end boost, because the ear reads definition as heaviness in a genre where the whole point is impact, not warmth.

The tell is a chugging low-string riff that turns to mud the instant a second rhythm guitar doubles it. Two takes of the same riff, even performed identically, sum their random phase differences into extra low-mid density a single guitar never had. Narrowing the double's pan slightly, or trimming gain-stage output before the amp sim rather than after, keeps the doubling wide without doubling the mud.

Where actual gain helps: a tight low end and a controlled top end. Where it stops helping: everywhere in between, because past a certain input level a distortion algorithm stops tracking pick dynamics and starts compressing the transient into a flat wall — and a flat wall reads as quieter than a riff with attack, even at the identical numeric level.

Snare Crack Versus Snare Body, and the Kick at Speed

Snare crack and snare body are two different frequency ranges doing two different jobs, and metal mixes lean hard on the first one. Crack lives around 3–6kHz — the stick transient, the thing that cuts through a wall of guitar and tells the listener a hit just happened. Body lives around 150–250Hz — the drum's actual pitch and sustain. A 4:1 ratio with a 20–30ms attack lets the initial crack through uncompressed and catches the body's decay a few milliseconds later; set the attack faster and the transient gets squashed along with everything else, and the snare stops sounding like it was hit.

Double-kick and blast-beat passages above roughly 200 BPM add a third problem: at that speed, individual hits start overlapping their own decay tails, and a release time set for a mid-tempo groove smears them into a low rumble with no separation between strikes. Shortening the compressor's release to 60–80ms on fast kick passages, sometimes automated section by section rather than set once for the whole song, keeps each hit distinct instead of building into a wash.

For an object lesson in how kick click resolves at speed, put on a Gojira track and listen to how much of the low end is click and air rather than boom — that's the same 2–4kHz definition doing the same job at a slower tempo, the only part of the kick's spectrum fast enough to resolve as sixteen notes instead of one droning pulse.

Cymbal Wash and the Fatigue Band

Cymbals in a dense AI-rendered mix tend to arrive as a continuous wash rather than distinct hits, because the model has no reason to leave the gaps a human drummer's stick control would naturally create. The 6–10kHz range is where that wash lives, and it's also the range most associated with listening fatigue over a full song length — too much energy there and a mix that sounded exciting for thirty seconds becomes exhausting by the second chorus. A gentle dynamic cut in that band, riding a few dB during the densest passages rather than a static shelf, keeps the cymbals present without keeping them constantly loud.

The other lever is separating wash from attack: the stick-on-metal transient sits closer to 8–12kHz, while the sustained shimmer that follows it occupies the same 6–10kHz zone as guitar pick noise and vocal sibilance. When all three compete, the cymbals usually lose intelligibility first, because they're the widest, least-focused source in the stack. Narrowing their stereo image slightly, rather than pushing them louder to compete, generally wins back clarity that boosting would only spend on making the fatigue problem worse.

What's Actually in the AI Stems

Suno rebuilt its stem separation on 11 June 2026, and the option chosen changes what's usable for a metal mix. Auto Split returns twelve stems for 50 credits — enough to separate drums, bass, and guitars, but not a rhythm guitar from a lead guitar within the same performance. Split from Mix pulls one chosen part plus everything else for 10 credits, useful for isolating just the bass or the kick when only one element needs rebalancing. Advanced Split, Premier-tier only, breaks a track into roughly a hundred instrument stems at 10 credits per stem — the only option that gets close to a genuinely multitracked session, though the per-stem cost adds up fast across a full arrangement.

Udio restricted stem export and download in May 2026 under its Universal Music partnership, so a track generated there arrives as a finished stereo file with no path back into its parts. That's a real constraint on a genre built around interlocking low end — a bass line and kick pattern that need frequency-slotting against each other can't get it, if they were never separable to begin with. The practical move for anyone writing in Udio and expecting a metal mix afterward is to treat the generation as an arrangement and tuning reference, then rebuild the parts — real guitar and bass DI, programmed or recorded drums — rather than expect the platform to hand them over later.

Loud Doesn't Win Anymore, and the Math Says So

Spotify normalizes every track to -14 LUFS integrated on playback; Apple Music's Sound Check targets -16 LUFS. Neither platform compresses anything to do this — it's a gain adjustment, turning the file up or down to match a target loudness, nothing more. A master pushed to -6 LUFS gets turned down roughly 8dB before anyone hears it; one left dynamic at -14 LUFS isn't turned down at all. Both end up perceived at the same loudness. The difference is that the brickwalled version already spent its kick and snare transients getting there, and gets none of it back on the way down.

True peak matters from the other direction: -1 to -2 dBTP of headroom keeps inter-sample peaks from clipping on playback systems that reconstruct the waveform between samples, which lossy codecs and many DACs both do. A master slammed flush to 0dBFS has no margin for that and can distort on exactly the systems fans are most likely using — earbuds, phone speakers, car audio.

This is the loudness-war argument, resolved by arithmetic rather than opinion, and metal has pushed harder against it than almost any other genre on the assumption that loud equals aggressive. It doesn't, post-normalization. A mix with real transient on the kick and snare, mastered to leave -1 to -2dBTP of headroom and landing anywhere competitive in LUFS, gets turned down slightly less than a brickwalled one and arrives with its impact intact. The loudness race only existed on platforms that played files back at their raw level — none of the platforms that matter now do.