Quiet Lab: DJ Beat Maker

A cat in headphones builds a track in front of you.

It starts with a hat. Then a kick, a snare, a bass line, a lead, one lane at a time, and it says what it just did as it goes. Techno starts on the kick instead, the way techno does. By the end the whole grid is lit and the cats are dancing, and it rides the finale until you pick another track.

MAKE YOUR OWN
Switch to Build and the screen becomes a small studio: the grid large, five strips with a level fader, mute and solo for kick, snare, hat, bass and lead, swing and tempo. Tap the cells you want, tap one again for an accent, press play, and it plays exactly what you put there. Pixel Cat stays in the corner and says what you just did.

YOUR OWN SOUNDS
Any lane can play a sound you made. Record a short take with the microphone, after a count-in, or bring an audio file in from Files. It is trimmed and levelled, and a bass or lead lane plays your one note at every pitch on the grid. Arrange sections over your beat, with risers and drops, or let it be laid out for you, and the clip opens on I MADE THIS BEAT, with your genre in the middle.

EIGHT GENRES, FIFTY SEVEN TRACKS
House, techno, dubstep, drum and bass, rock, trap, disco and lo-fi. Twelve techno tracks, nine house, six in each of the rest. Every one is its own pattern, most are their own key, and many bring their own tempo, kit and swing. A genre is not one song on repeat.

The first house, techno and lo-fi tracks are free to watch, so you hear what you would be paying for before you pay for it. Build mode and the other fifty four tracks come with the one payment.

A PIANO THAT PLAYS ITSELF
The third tab. Twenty classics fall onto the keys the way the reels do, most of them every note of the printed edition: Für Elise, Moonlight Sonata, Pathetique, Toccata in D minor, Rondo alla Turca, the Revolutionary Etude and fourteen more. Clip one and the cat nods through the outro. Für Elise is free.

NOTHING IN THE MUSIC IS A RECORDING
Every kick, snare, hat, bass note, lead note and piano note is generated in code as it plays, unless it is one you recorded or brought in yourself. There are no samples and no music files behind the DJ or the piano. None of it is licensed from anybody, and the tempo slider changes the music instead of changing its pitch.

TWENTY FIVE MACHINES THAT RUN THEMSELVES
The first tab is Simulations. Nobody aims, nobody scores, nothing to lose. You set a few numbers, press Play, and watch what the rules do.

Merge Flask. A stream that falls, fuses and climbs.
Crusher. Two arms press, and everything they squeeze makes more.
Ray Optics. Falling dots, one mirror, one focus.
Flood Race. One way down, a tide behind them.
Growth Chamber. It gets bigger every time it touches the wall.
Chord Web. Thousands of points off one circle, drawing as they go.
Rim Fill. A ring bounces, grows at every bounce, and fits.
Pendulum Wave. Fifteen swings drift apart and line up again, each a note.
And seventeen more.

MADE BY HAND
The physics is a s