Week 5: Time inside the instrument

Why an instrument with a clock of its own is a different kind of thing than one that only ever reacts

22 March 2027

Everything built in the first four weeks is a pure function of input: touch it, something happens; stop touching it, nothing does. That’s a reasonable instrument, and it’s also a limited one — ink doesn’t wait for you to decide it’s dry, and a held note doesn’t wait for you to decide it’s over. Giving an instrument its own advancing clock, independent of input, is what turns it from a responsive surface into a small dynamical system, with everything that implies: state that can drift, oscillate, or get stuck in a way no single input event caused.

That last part is the week’s actual warning. Once decay and input both write to the same piece of state, a bug where one path silently overrides the other becomes possible, and it’s a genuinely different failure mode from anything in weeks 1 through 4: a value can get pushed to a boundary by one path while looking, from the outside, like it’s simply obeying the other. Test for it by continuing to act after the suspicious state is reached, not by taking one screenshot and trusting it.

Outline#

• from pure reaction to a system with its own clock
• ink, charge, and other decay metaphors as the same mechanism
• the specific failure mode where decay and input fight over one value