ableton-bassline

name	Ableton Bassline
description	This skill should be used when the user asks to "write a bassline", "make a bass line from these chords", "give me a reggae/funk/house/lofi bass", "add bass to this progression", or wants an idiomatic bassline generated over a chord progression in Ableton Live. Writes a bass MIDI track that follows the harmony in a chosen style.
version	0.1.0

Ableton Bassline

Generate an idiomatic bassline that follows a chord progression, written as a MIDI track in the Live Set. The bassline is the soul of most genres — its rhythm and space matter as much as its notes.

When to use

Triggers: "write a bassline", "bass from these chords", "[genre] bass". For full arrangements use ableton-genre-cover; for the chords themselves use ableton-reharmonize.

Process

1. Use ableton-live-runner for build/run/kill + scaffold.
2. Get the progression — from a clip (read clip.notes, take the lowest/root per bar) or from text. Read the key (song.rootNote) and song.scaleIntervals to keep passing tones diatonic.
3. Pick the style feel (the defining choice). Apply its rhythm template, transposing the root per chord. Use low register (root around MIDI 28–40) and a fallback instrument list ending in Drift (["Operator","Drift"] — note "Bass" does not insert).
4. Add motion tastefully — passing tones into the next root, octave pops, ghost notes. Keep the genre's characteristic rests.
5. Write the track and shape tone with ableton-tone-recipes/ableton-fx-chain (Auto Filter to round, Compressor + Saturator to make it audible on small speakers).

Style rhythm templates (relative beats within a bar)

Style	Pattern (R = root, 5 = fifth, 8 = octave, · = rest)
Reggae one-drop	R · · 5 R · 8 · (leave beats 2 & 4 open — the breath)
Rocksteady/ska	R · R(&) 5(&) R · 8(&) · (bouncy, syncopated)
House	steady 8ths on root with off-beat octaves
Funk	syncopated 16ths, root + ♭7 + octave, ghost notes
Lofi	R(1, long) · · · R(2.5) · · · (deep, sparse)

Code pattern (generic bouncy example — adapt the rhythm to a table row above)

const ROOTS = [/* MIDI root per bar, e.g. */ 33, 33, 32, 37]; // octave pops (r+12) intentionally
                                                              // exit the bass register
function writeBass(notes, bars, bpb = 4) {
  for (let bar = 0; bar < bars; bar++) {
    const r = ROOTS[bar % ROOTS.length], b = bar * bpb;
    notes.push({ pitch: r,    startTime: b + 0,   duration: 0.45, velocity: vary(108, 3) });
    notes.push({ pitch: r,    startTime: b + 1.5, duration: 0.25, velocity: vary(90) });
    notes.push({ pitch: r,    startTime: b + 3,   duration: 0.40, velocity: vary(102) });
    notes.push({ pitch: r+12, startTime: b + 3.5, duration: 0.25, velocity: vary(84) }); // octave lift
  }
}

Limits

• "Bass" device fails to insert; use Operator/Drift + Auto Filter to round the tone.
• Keep it deep but out of the kick's way — leave space (sparse beats out-groove busy ones).

See ableton-reharmonize, ableton-tone-recipes, ableton-drum-groove.