Polymetric sketches

1. Set the global controls. At the top of the page, set your base tempo in bpm, select a beat unit, and set the window length in seconds. A typical starting point is ♩ = 52, ♩=4, 60 sec.

2. Work on the tracks. The left sidebar lists your tracks. Click + add track to create a new layer. Each track is given a distinct color from the Preplan palette (ochre, teal, lavender, sage, rose, golden) and an auto-generated name like "Voice A". Rename a track by clicking into its name field.

3. Author segments. Inside each track, each card represents one segment with three fields: count × num / den. Change numbers directly, or pick the denominator from the dropdown (1, 2, 4, 8, 16, 32). Reorder segments with the up/down arrows, remove with the trash button, and add more with + add segment. The readout below the card shows the bar duration in milliseconds and the segment's cumulative contribution to the loop.

4. Read the timeline. The right pane shows every track as a horizontal lane. Downbeat ticks appear in the track's color; loop boundaries are tall ticks labeled with their time signature (e.g. 5/8). Hover over any tick to see a readout below: track name, bar number, time signature, absolute start time, and bar duration in milliseconds.

5. Inspect the loop periods. Scroll down below the timeline to see a card for each track listing its period length and how many times the loop fits in the window. This is where you diagnose whether your layers settle into a long common cycle or drift continuously.

The simplest polymetric pattern. Voice A plays twelve bars of 3/4; Voice B plays twelve bars of 4/4 at the same tempo. Voice A's loop completes in 36 quarter-note beats; Voice B's loop completes in 48. The two lines realign every 144 beats (the LCM).

In the timeline you will see Voice A's downbeats land three-for-every-four of Voice B's. Coincidences appear at every bar of Voice B that also happens to be a bar of Voice A — which, for this combination, is every fourth bar of A and every third bar of B. Set the window to 60 seconds and watch the coincidence density thin out as the layers drift.

This is a useful warm-up sketch: it tells you how long a full polyrhythmic cycle actually takes before you commit to any pitches.

Two tracks with complementary irrational meters. Voice A's loop is 35 eighth-notes long; Voice B's loop is also 35 eighth-notes long — so the two layers realign exactly at each full loop. Between realignments they drift through an evolving sequence of offsets.

Set the beat unit to ♩=8 so the eighth-note gets the tempo beat. You should see a coincidence at every loop boundary plus a few internal ones where the 7-grouping and 5-grouping briefly line up. This is the engine behind a lot of Balkan-tinged and post-minimal writing.

To make it breathe, add a third track with an unrelated length — try Voice C: 3x11/8. The three-way realignment cycle is now much longer, and the coincidence map becomes a compositional feature in itself.

This is the default sketch that loads with Preplan. Each track is itself a meter sequence — not a single repeating bar but a through-composed cycle that restarts after all segments have played. The two voices have different total durations so they gradually shift against each other every time one loop completes before the other.

Look at the loop-start markers (tall ticks with time signatures) — you will see Voice A announce 4/4, then 7/8 four bars in, then 5/8 seven bars in, then restart with 4/4. Voice B does the same with its own segment sequence. The two tracks slide in and out of alignment across the whole window.

This is the architecture Ligeti used in San Francisco Polyphony and the first book of Pétudes — independent metric lines that share a pulse but never settle into a common bar. Use send to Compose to turn the sketch into a movement, then develop each voice's pitch content independently in the Graph view.

A single-track sketch used to plan an accelerating surface. The base pulse stays the same (♩=60) but the bar length shrinks progressively: four bars of 4/4, then four of 3/4, then 2/4, then 1/4. Downbeat density doubles by the end of the loop.

Use the readout to see bar durations drop from 4000 ms (4/4) to 1000 ms (1/4). This is a compositional strategy for notating a gradual acceleration as a meter ramp instead of a tempo change — players count the same beat throughout, but the music gets denser because bars arrive more frequently.

Mirror the ramp on a second track with the reverse sequence (4x1/4, 4x2/4, 4x3/4, 4x4/4) to create a converging-then-diverging density pattern across two voices — a useful texture for duo passages.

A minimalist-style pair where both tracks reuse the pair of numbers {7, 11} but in swapped positions. Voice A's loop is 7 × 11 = 77 eighth-notes; Voice B's loop is 11 × 7 = 77 eighth-notes. They realign every 77 eighths — roughly every 24 seconds at this tempo — but the barline patterns inside that cycle are completely different.

The coincidence dots at the bottom of the timeline will be sparse in the middle of each cycle and clustered at the loop boundaries. This is the effect Reich and Adams exploit when two lines share an overall period but differ in their internal bar groupings.

Once the sketch feels right, send to Compose. Add a third voice in a related meter (say Voice C: 5x7/8, 5x11/8) to introduce a drifting contramotion on top of the realigning pair.