1) Infinite Bars (what you’re seeing)

The grid is a moving window into an infinite timeline. We render N bars (default 16) starting at a bar index derived from the current playhead. Under the hood, bar indices can go on forever (0…∞).

2) The Seed (determinism)

The Seed is the root of all randomness. We use a small PRNG (fast, repeatable) so the same seed produces the same “random” decisions every time. Change the seed → the song changes, but remains coherent.

• Same seed + same sliders ⇒ identical bar placements.
• Different seed ⇒ new placements, same rules.

3) Lane Seeds (so each lane feels unique)

Each lane derives its own “sub-seed” from the root seed, lane id, and bar index. Conceptually:

laneSeed = mix(seed, hash(laneId), barIndex)
rng = PRNG(laneSeed)
              

That means KICK, SNARE, HAT, BASS can each have distinct behavior while staying locked to the same global seed.

4) Occupancy Grid (your “don’t overwrite this lane” rule)

For every lane and bar we build an occupancy grid of steps (16 steps per bar by default). We pre-fill it with:

• Locked events (you clicked/placed them).
• MIDI events (imported).

Then we check the lane-bar count: If the lane has zero events in that bar, we auto-fill using math. If the lane already has events, we do not overwrite them.

5) Density sliders (how many hits get placed)

Density is a probability/target controller. Higher density means more steps are likely to become hits, but only into free slots. We never place two hits on the same step.

6) Swing (timing feel)

Swing delays every other subdivision slightly (classic groove). It changes scheduling time, not bar math. In other words: placements stay the same, but the “off steps” happen a little later.

7) Scheduling (why it stays stable)

Audio is scheduled with a look-ahead window (we schedule slightly ahead of the playhead). This avoids glitches and ensures timing stays tight even if rendering lags.

8) What’s Generated vs Locked vs MIDI

• Generated: created by math from seed + rules; can be regenerated.
• Locked: your manual placements; never change unless you edit them.
• MIDI: imported note events mapped into a lane; treated as “occupied” so autofill won’t overwrite that bar.

9) Practical workflow

1. Pick a seed (or randomize) until the groove is right.
2. Set lane densities (kick sparse, hat busy, etc.).
3. Lock any “must keep” hits by clicking the grid.
4. Import MIDI for a lane if you want a fixed pattern there.
5. Export preset (seed + rules + locks) and reuse it anywhere.