drum-apparatus

name

drum-apparatus

description

Program heavy / death-metal drums into the user's live REAPER session the way David does it — kicks built off the guitar riff first, snare by his call, cymbals by feel, spicy fills, humanized at placement time. Use when the user asks for a drum groove, beat, blast, breakdown, fill, or a multi-section drum part, or says "give me a <subgenre> groove" / "program drums for this riff". Drops generated MIDI into REAPER via the agent bridge.

Drum Apparatus — David's drum-programming SOP

This is how David programs drums. Follow the order. The cardinal sin is starting from a named groove in the catalog — David does NOT think that way. He builds the beat from the riff up. The catalog is a vocabulary to reach into mid-build, not a menu to order from.

The procedure (in this order, always)

1. Kicks first — built off the guitar riff

Drums start as kicks ALONE, matched to the guitar. David tracks the guitar as audio before drumming.

• Find the riff's guitar take (he points you at the track, or it's the obvious guitar audio item under the cursor) and read its transients to get the hit timing, quantize to the grid, and propose kicks on the strong/open hits.
• HONEST LIMIT: transients tell you when he picks, not which notes ring open vs palm-muted. So this is a proposal he corrects, not a magic auto-beat. Show the kick grid, let him fix the few you get wrong. That's still miles faster than him describing a riff in words (which he says is basically impossible).
• If there's no guitar take yet (drums-first), ask him for the kick rhythm. Don't invent one.
• Transient reading: python3 reaperd.py riff <project.RPP> <track> [--bars N] [--start-bar N] (parses the .RPP for the track's stem, detects onsets, prints the kick grid at 100/50/30% attack strength).
• Kick density = a real flavor choice (David's words):
  • Slam / breakdown (his DEFAULT): one single kick per transient. Sparse, heavy, slamming. Use a LOW keep_pct (~30) so only the strong open hits become kicks. This is how David's own hand plays it.
  • Gallops / triplets: keep_pct=100 turns every pick attack into a kick, so a fast riff reads as gallops/triplets. David does NOT instinctively do this but LIKES being pushed to it ("not what I would've done, but that's why I like it"). Offer it as the adventurous option, don't make it the default.
• Phase calibration: the grid is anchored to item time 0; a stem's real downbeat can sit a step off. GTR_1 read one 16th early -> pass offset_steps=1. Per stem, so check the first render against the riff and adjust.
• It's a PROPOSAL David corrects (the percentile is a strength heuristic, not true open-vs-muted). He has ears; let him pick density and dial the offset.

2. Snare — David calls it, every time

There is no default snare placement. It's pure feel and it sets the whole section's pace and feel. Once kick + snare are down, the backbone is LOCKED — you do not go back and move kicks.

• ASK for the snare placement, or take what he gives. Never guess it.
• If he describes it loosely ("backbeat", "half-time", "on the e of 3"), place that — but the call is his.

3. Cymbals — the feel knob, by ear

Kick + snare are the backbone; the cymbal choice is what sets the mood. There is no fixed section→cymbal rule (the old rigid table was wrong). It can be anything, and it's usually several cymbals at once.

• Hi-hats → more mellow groove. Crashes / chinas → loud, lots of noise.
• The ONE default: in heavy parts, steer away from closed hi-hats unless he asks — closed-hat breakdowns are the off-putting tell of a bad beat.
• Verses lean open hi-hat, but crashes and ride are all fair game.
• Breakdowns lean china + crash on the stabs, never a hat grid. (See Breakdowns below — they're not grooves.)
• When in doubt, ask which cymbal. It's a taste call, not a rule.

4. Fills — last, and get spicy

Fills go in last, after the backbone and cymbals. Default placement: at the end of a section/phrase, to break up the energy and lead into what's next. Frequency is mood-dependent — some songs only use fills to bridge sections, others are stuffed with them; both are good.

• David LOVES fills but hates writing them: be creative here. This is the one place to be inventive, not conservative. Roll across the kit, vary it, surprise him.
• Fill velocity shape: start lower, ramp up across the kit — especially coming off the highest tom, low→high gives the real rolling sound.

Humanization — the golden rules (applied at placement time)

David humanizes as he places each note (nudging velocity 2–3 notches per hit), not in a final pass. So the engine bakes these in at render time — the output is already humanized, nothing to fix after. These are physics, not taste:

1. No two consecutive hits in a lane are EVER the same velocity — differ by at least 1. Identical velocities = the machine-gun tell. (in code: groovekit velocity model)
2. A cymbal that lands together with a shell (kick/snare/tom) is louder — a human pushes harder on the cymbal because he's also hitting a shell. (in code: groovekit CYMBAL_SHELL_BOOST)
3. Hi-hat has its own curve: closed = softer, open = louder. Never one flat hat velocity, never just two alternating. (in code: groovekit HAT_CURVE)
4. Double kick: every 2nd kick is −7…−9 lower (weaker left foot). ONLY on fast double-kick parts where both feet are truly used — not slow single-foot kicks. (in code: groovekit run-scoped −7…−9)
5. Blast-beat snare arcs down over time, then lifts at the end — blasts exhaust the forearms so intensity sags, then he digs deep to finish. (pending)
6. Fills ramp low→high across the kit. (author the fill into the DSL grid — roll across the toms, ramp low→high; the engine humanizes velocity + timing)
7. Don't omit a cymbal where one is obviously called for. Bare focal snare hits are the bug. Passing accents in a flurry can be bare (more is coming right after); the focal hits want something with them. (judgment — apply by ear; the engine also FLAGS bare focal snare/cymbal hits as warnings — groovekit exposed_focal_hits — so they surface for review)

Velocity targets & per-kit voices (David's mix preferences)

• Kicks stay under ~114. Punchy, not maxed. (in code: groovekit KICK_VEL_MAX, per-render override kick_vel_max)
• Monarch kit → rimshot snare, held 90–110. The rimshot is fuller/louder; it's his go-to snare on Monarch, and it runs hot (loud-as-fuck by design). (in code: groovekit VOICE_PROFILE["RS Monarch"])
• These live in VOICE_PROFILE (per map) + KICK_VEL_MAX in groovekit.render. As new kits get preferences, add a profile entry — don't hardcode in the render loop.

Ground truth from David's own part (reverse-engineered, Monarch)

Decoded from a full part he programmed by hand (skill-build.RPP, bars 1–4). Treat as the reference for how his layers actually behave:

• Every snare and every cymbal lands ON a kick — 100% coincidence in the sample. Focal hits are never bare; a shell is always under them. This is the hard form of the "snare/cymbal never alone" rule (#7) and the cymbal-with-shell rule (#2).
• Cymbals are the loudest layer and they drive. Crashes 101–117, china 116, a double-crash (CRASH_R+CRASH_L stacked) on the big accent, china+crash on the section-end stab. Snares 90–110 and toms 92–106 sit underneath. Cymbals are not garnish — they're the top of the dynamic stack.
• Snare placement is by feel, not a fixed backbeat (landed on 1.4, 2.3, 3.1, 4.1, 4.3), and he'll drop a 16th-apart double rimshot for flavor.
• Loud sections = a crash wall on ~8th spacing, never a hi-hat grid.
• Tom fills roll across the kit with velocity ramping up (observed 92→106).

Generate & insert

1. Compose the section(s) as a spec or DSL once kicks/snare/cymbals/fills are decided (sections with bars, per-section power_hand / fill).
2. Generate + insert: python3 reaperd.py groove <dsl> --track <name> renders humanized MIDI and inserts it in one round trip.
3. Insert on the track David SELECTED (or --track <name> if he names one). NEVER guess a track.
4. VERIFY AUDIBLY (hard gate): set the cursor to the clip, play, and ask if it sounds right. NEVER claim a beat is good without his ear. Parse-back proves the notes exist, not that it slaps.

Params that matter

The live engine (groove + the DSL) exposes: @tempo, @map, @seed, per-section bars / feel (pp-fff) / grid, and the cell articulations (x hit, X accent, o ghost, f flam). Humanization (velocity model, fatigue envelope, weak foot, golden rule, timing jitter) happens in the engine at render time — there are no humanize / push_pull / power_hand / fills knobs (those belonged to the removed legacy renderer). Tighter or looser: change feel or re-roll @seed; write fills as explicit lanes.

Breakdowns (read this — they are NOT grooves)

A breakdown is spaced stabs + silence + naked kick chug, with a cymbal on the BIG accents only (the stab, the snare smash) — not a steady groove with a hat. Use the breakdown grooves that carry a cymbal accent lane: "World Ending Stomp" (2-bar) and "Chug Breakdown" (1-bar). The cymbal lane auto-suppresses the power-hand grid. Keep the stabs tight (low @feel, no fills) and render with reaperd.py groove. The named patterns ("World Ending Stomp", "Tight Chug Breakdown") live in catalog/grooves.json — reach in and transcribe. Authoring your own: add a cymbal step-string (X=crash, C=china, p=splash, r=ride, b=bell, -=rest) same length as kick; 2-bar (32-step) patterns work, cross-bar indexing handles it.

Catalog (vocabulary, not a menu)

50 grooves across 10 subgenres (DEATH METAL, SLAM DEATH, BLACK METAL, GRINDCORE, METALCORE, DOOM & SLUDGE, PROGRESSIVE METAL, ROCK, THRASH METAL, BREAKDOWNS) in catalog/grooves.json. Reach into these for patterns mid-build — but the beat is built from the riff (step 1), not selected from this list.

Drum kit maps (MIDI note assignments)

catalog/maps.json maps drum roles (KICK_R, SNARE, etc.) to MIDI notes. --map <name> selects one. Ships with GM Standard plus example library maps (RS Monarch, Odeholm Default, MDL Tone, Sleep Token II). python3 reaperd.py list-maps lists them. If the kit isn't there, auto-discover from its .midnam: python3 reaperd.py discover-map Drums --save MyKit. For kits with no .midnam (some Kontakt libs), ask for the notes: reaperd.py add-map MyKit --roles '{"KICK_R":36,"SNARE":38,...}'. Discovered maps save to the gitignored user overlay, so git pull never clobbers them.