write-trap-album

# Write Trap Album Use this skill for **melodic trap** (Lil Baby, Roddy Ricch, Drake trap-soul), **drill**, and dark minor trap. Half-time feel. Uses **CoupledHMMHarmonizer** + **chord-tone-contour harmony** + **manual MixingDesk/MasteringDesk**, with dedicated trap generators (`Bass808SlidingGenerator`, `TrapDrumsGenerator`, `HiHatStutterGenerator`). ## 1. Profile choice: `pop` (triadic) vs `funk` (transitions) Trap harmony is minimal, so the choice is about **what color you want**, not complexity: | Goal | Profile | Result | |---|---|---| | **Static dark trap**, clean minor triads (Cm–Ab–Eb–Bb) | `pop` | major triads intact, no 7th color | | **Melodic trap with transitions** (secondary dominants G7/Bb7 + dark m7 sonority) | `funk` | m7 + dom7 retained, but **major triads get absorbed into m7** (see pitfalls) | - `pop` = `completion_bonus=0` → clean triads only. - `funk` = `{8:5, 7:4}` → retains dom7 (type 8) and min7 (type 7). - **Trade-off (important):** the `funk` min7 bonus **captures spelled major triads into the m7 a fifth below**, because a major triad's tones are a subset of that m7 (Ab `[8,0,3]` ⊂ Fm7 `[5,8,0,3]`). So with `funk`, expect a lush all-minor/m7 texture with dom7 tension chords, NOT major/minor contrast. For major/minor contrast, use `pop` (but you lose dom7 transitions). You cannot cleanly have both. ## 2. Chord-tone contour — static axis vs through-composed **Static axis** (C minor i–♭VI–♭III–♭VII, the rap/trap axis), repeated: ```python KEY = Scale(root=0, mode=Mode.NATURAL_MINOR) FORM = ["i","bVI","bIII","bVII"] # loop these 4 bars ARP = {"i":[0,3,7], "bVI":[8,0,3], "bIII":[3,7,10], "bVII":[10,2,5]} # Cm / Ab / Eb / Bb # config=harmonizer_profile("pop") ``` **Through-composed** (interesting transitions): write a longer `FORM` with no exact repeat — mix in secondary dominants (`V7`/`V7iv`) and a Neapolitan (`bII`) across contrasting sections. Use the `funk` profile so the dom7 transitions retain: ```python FORM = [ # A: dark axis (0–15) "i","bVI","bIII","bVII", "i","bVI","bIII","bVII", "i","bVI","bIII","V7", "i","iv","V7iv","i", # T: chromatic transition (16–23) "iv","V7","i","bVI", "bII","V7","i","V7iv", # B: lift (24–35) / O: cadential outro (36–47) ... ] ARP = {"i":[0,3,7,10], "bVI":[8,0,3], "bIII":[3,7,10], "bVII":[10,2,5], "iv":[5,8,0,3], "V7":[7,11,2,5], "V7iv":[10,2,5,8], "bII":[1,5,8]} # config=harmonizer_profile("funk") ``` (See `scripts/albums/trap/melodic_trap_180.py` for the full 48-bar worked example.) Only spell chord types `funk` can anchor: **min7 / dom7 / major triad**. Avoid maj7 and half-dim (ø) — `funk`'s bonus set can't pin them and they collapse ambiguously. ## 3. Required imports + pipeline ```python import random, sys, warnings from pathlib import Path REPO = Path(__file__).resolve().parents[3]; sys.path.insert(0, str(REPO)) warnings.filterwarnings("ignore"); random.seed(41) from melodica.harmonize.coupled_hmm import CoupledHMMHarmonizer from melodica.harmonize import harmonizer_profile from melodica.generators import GeneratorParams from melodica.generators.bass_808_sliding import Bass808SlidingGenerator from melodica.generators.trap_drums import TrapDrumsGenerator from melodica.generators.hihat_stutter import HiHatStutterGenerator from melodica.generators.piano_comp import PianoCompGenerator from melodica.generators.solo_melody import SoloMelodyGenerator from melodica.generators.ambient import AmbientPadGenerator from melodica.shorts_mixing import MixingDesk from melodica.shorts_mastering import MasteringDesk from melodica.midi import export_multitrack_midi def _mix(raw, bpm, gains, lufs=-14.0): desk = MixingDesk(niche_cfg={}); desk.track_gains.update(gains) mixed = desk.apply_mixing(raw, [], int(bpm)) mastered, _cc = MasteringDesk(target_lufs=lufs).apply_mastering(mixed) # tuple return mastered ``` ## 4. GM programs `SYNTH_BASS=38` (808), `DRUMS=0`, `SYNTH_PAD=88`, `EPIANO=4` (Rhodes, to make chords audible), `LEAD_SYNTH=85`, `CLEAN_GUITAR=27`. ## 5. Generators (verified kwargs) ```python bass808 = Bass808SlidingGenerator( GeneratorParams(density=0.40, key_range_low=24, key_range_high=40), pattern="trap_basic", slide_probability=0.50, octave_range=2, ).render(chords, key, dur) # 808 sub-bass with pitch slides drums = TrapDrumsGenerator( GeneratorParams(density=0.40), variant="standard", hat_roll_density=0.60, kick_pattern="standard", open_hat_probability=0.20, groove_swing=0.50, ).render(chords, key, dur) # full trap beat (kick/snare/hats w/ rolls) hats = HiHatStutterGenerator( GeneratorParams(density=0.25), pattern="trap_eighth", roll_density=0.40, open_hat_probability=0.15, ).render(chords, key, dur) # extra hat rolls (optional; TrapDrums already has hats) comp = PianoCompGenerator( GeneratorParams(density=0.26, key_range_low=48, key_range_high=72), comp_style="pop", voicing_type="close", accent_pattern="syncopated", chord_density=0.45, ).render(chords, key, dur) # makes chord changes audible under 808+drums pad = AmbientPadGenerator( GeneratorParams(density=0.08, key_range_low=36, key_range_high=60), voicing="spread", overlap=0.4, ).render(chords, key, dur) lead = SoloMelodyGenerator( GeneratorParams(density=0.22, key_range_low=60, key_range_high=84), style="blues_lick", blues_notes=True, chromaticism=0.30, vibrato_depth=0.3, ).render(chords, key, dur) # autotune-style melodic hook ``` ## 6. Subgenres | Subgenre | Key | BPM | Profile | Form | LUFS | Example | |---|---|---|---|---|---|---| | Melodic trap (static) | C minor | 140 | `pop` | i-♭VI-♭III-♭VII axis | -14 | `scripts/albums/trap/melodic_trap.py` | | Melodic trap (through-composed) | C minor | 180 | `funk` | 48-bar 4-section, transitions | -14 | `scripts/albums/trap/melodic_trap_180.py` | | Drill | Cm / Fm | 140–145 | `pop` | minor axis, sliding 808 | -14 | — | > BPM is the **true** tempo; trap is felt half-time (140 ≈ 70, 180 ≈ 90). Hat rolls get denser at higher BPM — lower `hat_roll_density` if it clutters. ## 7. Pitfalls | Issue | Fix | |---|---| | Major triads (Ab/Eb/Bb) turned into m7 | That's `funk`'s min7 bonus capturing them (Ab ⊂ Fm7). Use `pop` if you want major/minor contrast; accept all-minor if you want dom7 transitions. | | Neapolitan ♭II (Db) disappeared | Same capture (Db `[1,5,8]` ⊂ Bbm7). Only spell chords `funk` can anchor (min7/dom7/maj triad); avoid maj7 & ø. | | Hats too busy at high BPM | `TrapDrumsGenerator` already includes hats — skip `HiHatStutterGenerator`, or lower `hat_roll_density` / `roll_density`. | | Chord changes inaudible | Add a `PianoCompGenerator` (Rhodes) comp track so harmony is heard under the 808+drums. | | Track transposed | Contour base must be a multiple of 12. | | `MasteringDesk` crash | Returns tuple `(mastered, cc)` — unpack. |