The garden that plays itself

The first two chapters of this part recirculate sound: tape that forgets, loops that never agree. This one recirculates decisions. Plant a note and it comes back every pass of the loop a step quieter and a step purer, until it fades below hearing and retires. Plant several and they braid. Stop planting altogether and, after a patient interval, the garden starts planting for itself — always on the scale, never in a hurry. You do not play this instrument so much as tend it, which is exactly the posture Eno kept asking for: the composer as gardener, not architect. The kernel is named for that metaphor.

What it recreates is the principle behind Brian Eno and Peter Chilvers' generative apps (Bloom, 2008), as described in their published interviews and in Eno's 1996 "Generative Music" talk: touch becomes note, note repeats and fades, scale makes wrong notes impossible, idleness hands the piece to the system. The principle only — no scale tables, timings, or sounds are taken from the app, and its name is a live trademark of Opal Limited, which is why this object is a garden and not a bloom. (As with tap.tune~'s history paragraph, none of this is legal advice; the project's ship-gate is a freedom-to-operate review.)

Companion material: the executed notebook garden.ipynb, which measured every claim below, and the eno_render tool's garden_played and garden_idle scenarios, the listening copies. The Max wrapper lands in the TapTools-Max package alongside the rest of the family.

Events on a loop instead of audio on a tape — the same recirculation, one level of abstraction up.

Plant and return

note(pitch, velocity) plants: the pitch snaps to the current root and scale at entry, a soft two-operator FM bell sounds on the next sample, and the event takes a seat at the loop's current position. Every pass, it fires again at velocity × decay, and below floor it retires. The notebook's staircase is the whole contract in one figure: a plant at 0.8 with decay 0.5 returns at 0.795, 0.399, 0.2, 0.1, 0.05 — then silence, and active_events reads zero.

The return staircase: decay 0.5, floor 0.05, and a bloom that knows when it is finished.

That arithmetic is also the stability story. The family's inversion — degradation as the stabilizer — reaches its third form here: a bloom lives exactly ceil(log(floor/velocity) / log(decay)) passes, so the population of live events converges by construction no matter how fast you plant. And beneath the arithmetic sits a hard bound: sixteen bells in a fixed pool, the quietest stolen when a seventeenth is needed, its envelope re-aimed rather than reset so a steal glides instead of clicking.

soften — returns get purer, not just quieter

Each pass also multiplies the event's brightness by soften, and brightness is the bell's FM index: the upper partial fades while the fundamental holds, so a bloom collapses toward a sine as it recedes — the tape chapters' generation loss, restated in partials instead of passbands. The notebook measures the sideband-to-fundamental ratio shrinking every single return, and the pinned test requires it strictly.

The scale contract

root and scale (chromatic, major, minor, and both pentatonics — plain public-domain scale theory) define where plants may land, and quantization happens at entry: the notebook plants all thirteen chromatic pitches from 60 to 72 into a C major-pentatonic garden and the YIN oracle reads every sounded note on {C, D, E, G, A}. Wrong notes are not discouraged; they are unrepresentable, which is most of why instruments in this family feel effortless to strangers. Because quantization is at entry, changing the scale re-pitches nothing already planted — the field changes for future seeds only.

The gardener

idle_seconds is the patience: that long after your last plant, the garden begins seeding itself, roughly one note per loop pass, uniformly placed, on the scale, within two octaves. The randomness is the family's seeded xorshift64* with the full tr808 contract, pinned as a triad: same seed, bit-identical garden; different seed, a different garden; gardener disabled (idle_seconds 0), the seed cannot matter at all, because the generator is never consumed. This is the library's first randomized event source — step_seq.h proudly promises "no randomness anywhere" — and the seed contract is what lets a generative instrument live in a test suite that demands reproducibility.

Recipes

• The lobby: defaults, @idle 30. @level 0.4, plant four or five notes, walk away. The garden holds the room indefinitely, bounded.
• The music box: @decay 0.5 @soften 0.7 @idle 0 @bell 0.005 0.8 1. — no gardener, fast decay: each phrase you play unwinds itself to silence in a few passes, a wind-up toy running down.
• The endless install: @scale minorpentatonic @root 2 @idle 3. @seed 2008 @level 0.35, never touch it again. Same seed next year, same garden.
• Duet: @idle 6. and stay at the keyboard — every silence longer than six seconds, the gardener answers you; every plant of yours resets its patience.

When it is not the right tool

• Melodies with wrong notes in them. Quantization is always on; chromatic passing tones survive only in @scale chromatic, and micro-tonal pitches not at all. This is a fence, and it is the product.
• Rhythm. Events return on the loop grid, exactly, forever — no swing, no humanization. For patterns as rhythm, tap.808.seq~ is the machine.
• Any other timbre. One soft bell family, on purpose. It is an instrument, not a polysynth; for FM as a playground, patch oscillators.

Checkpoint

Notes become events; events recirculate on a loop, quieter by decay and purer by soften each pass, retiring below floor; a sixteen-bell pool bounds the sound and a sixty-four-seat ring bounds the score, oldest bloom yielding first. The scale makes wrong notes unrepresentable, and a seeded gardener keeps the piece alive exactly as long as you neglect it. Every number above lives twice: as an executed cell in garden.ipynb and as a pinned scenario in tests/garden_test.cpp, which CI runs on every push.