Two circles. Two thumbs. Tap however you like — and the music finds you.
Rhythumb is a fidget you play with both thumbs. There is nothing to read and nothing to set up: touch the screen and it answers. Keep going and it listens for the rhythm you are already tapping, then builds music around it — a pulse, then a warm low note, then a chord, then something bright on top.
It never asks you to keep time. If your rhythm wanders the music simply thins, and it thickens again when you settle. There is no way to get it wrong, because there is nothing here to get wrong.
As you play, the sky travels. The field opens out, thickens into cloud, empties into a long dark, and fills again — and the music moves with it. Nothing is named and there is nowhere to arrive, so a session that lasts forty seconds has travelled just as truly as one that lasts three minutes.
After about three minutes — or whenever you ask, or simply stop — Rhythumb winds down. The music leaves in the order it arrived, the light dims and slows, and the circles breathe at about five and a half breaths a minute, in case you would like to breathe with them. Then it offers you the choice to carry on, or to be done for now.
It also offers you the session itself. Every time you play, Rhythumb quietly remembers what you made, and at the end you can keep it — a short piece of music that exists because of how you happened to tap that day. There is no record button, because a record button would turn a session into a take, and takes can be spoiled.
Rhythumb honours Reduce Motion and Reduce Transparency, and everything it says can be read by VoiceOver. A Still setting stops the scene drifting for anyone who finds movement distracting, and one control scales the sound, the light and the strength of the haptics together.
Rhythumb is in testing. It is made for iPhone, runs entirely on your device, and will be available on the App Store soon.