Tessellator plays two tones at once, one in each ear, and draws them as a Lissajous figure. The first tone moves a point of light side to side, the second moves it up and down, and the path the point traces is the figure. The shape you see is the sound: change one tone and you change the other. Everything is generated live as you play.

What makes the figures musical is that the same simple ratios that make intervals sound smooth also draw simple, steady shapes. Two tones whose frequencies have a ratio of 1 to 2, an octave, trace a figure-eight. More complex ratios trace busier patterns. When the two tones drift slightly out of tune, the figure slowly turns, and you can hear that same drift as a gentle pulse.

Use headphones for the full stereo experience. Each ear hears its own tone.

What you're seeing

• The figure: the bright gold Lissajous curve traced by your two tones. It redraws continuously as you play, so it always matches what you hear.
• The glow: brightens as the sound gets louder.
• Ghost curves: faint copies beside the figure, from the Thickness setting.
• Grid labels: the small labels along the edges show what each direction controls, such as note names for pitch.
• The readout: the current interval and its two frequencies. In Keys mode it shows the note you're holding; with the arpeggio running, it shows the chord and note.
• A gold dot on the play mode icon: the arpeggio is running.

Recording

Tap the red dot to start recording, and tap it again to stop. When you stop, your phone's share options appear, so you can save the recording to Files, AirDrop it, or send it in a message.

• The recording starts at your first sound.
• It captures the instrument's sound directly, not through the microphone, so room noise never gets in.
• It records the sound only, not the figure.

Three modes to play

• Touch: press and drag anywhere on the grid. Where your finger is sets both directions at once. Lift off and the sound stops.
• Keys: play the keyboard, or slide across it to play every key you pass. The arrows at each end change the octave. The grid still shapes the sound.
• Drone: tap Start drone for a continuous sound, then shape it on the grid while it plays.

The grid's two directions

Each direction can control one of seven things, chosen in Settings:

• Pitch: the note. Moving across the whole grid spans one octave.
• Volume: loudness.
• Phase: shifts the figure's loops. It changes the picture but barely the sound.
• Brightness, Thickness, Drift, or Tremolo: the Tone controls, explained under Sound.

When the grid controls a Tone setting, its slider dims and shows "X axis" or "Y axis" instead of a value.

The interval, the relationship between the two tones, decides the Lissajous figure's shape. The two numbers are the ratio of the tones' frequencies: in 2/3, the first tone completes two cycles in the time the second completes three. The smaller the numbers, the simpler the shape and the smoother the interval sounds.

• 1/1 Unison: the same note in both ears. Pure and centered.
• 1/2 Octave: the same note, higher. The most stable interval.
• 1/3 Twelfth: an octave plus a fifth. Open and hollow.
• 2/3 Perfect fifth: strong and steady.
• 3/4 Perfect fourth: wide and slightly unresolved.
• 3/5 Major sixth: warm and sweet.
• 4/5 Major third: bright and happy.
• 5/6 Minor third: darker and melancholy. The busiest figure.

Phase shifts the loops without changing the pitch. At unison, it opens the line into an ellipse or a circle.

Waves

X is your left ear and Y is your right. Each wave sets both that ear's tone and how the figure is drawn in that direction.

• Sine: round and pure. The softest.
• Triangle: soft with an edge, a little like a flute.
• Square: hollow and buzzy, like a clarinet or a retro video game.
• Sawtooth: the brightest and buzziest, like brass.

Classic Lissajous figures use sine waves on both sides. The other waves bend them into shapes of their own.

Tone

• Brightness: from dark and muffled to bright and open. It has little effect on sine waves, which are already pure.
• Thickness: a chorus effect that makes the sound wider and fuller.
• Spread: how separate your two ears are. At 100%, each tone stays in its own ear; at 0%, you hear both tones in both ears.
• Drift: makes the figure slowly turn and the two tones pulse against each other. Most of the slider covers slow, subtle motion.
• Tremolo: a pulse in the volume that gets deeper and faster as you raise it.

Turn it on in the mode panel. It plays a chord one note at a time, and the figure changes shape on every step.

• Chord: follows the Scale in Settings. Major and Minor play the root, third, fifth, and octave; Pentatonic adds the sixth.
• Pattern: Up, Down, Up-down, or Random.
• Speed: 40 to 200 BPM.

It plays whenever sound is playing: while you hold the grid or a key, or while a drone runs. To stop it and keep the current shape, tap any shape in the Figure panel.

Tap the preset name under the figure to browse ready-made sounds. Tap a preset to hear it, and keep tapping to compare. Reset returns to the default sound and settings.

• A gold dot beside a preset means it comes with an arpeggio.
• "· edited" after the preset name means you've changed something since loading it.

Drone presets start playing when you tap the play button. Presets never change your master volume.

• Base note: the note the grid starts from, from A2 to A4.
• Scale: Major (bright), Minor (darker), or Pentatonic (every note fits). It also sets the arpeggio's chord.
• X axis and Y axis: what each direction of the grid controls.
• Pitch glide: Stepped snaps to the notes of the scale; Smooth slides through every pitch in between.
• Output: Stereo sends each tone to its own ear; Mono blends both tones together in both ears.
• Master volume: the app's overall level.