Most voice notes start in a hurry: walking, driving, half-asleep. So the record button has one job, which is to be found without looking.
How we tested it
Forty people used prototypes for a week. We logged every missed tap and asked them to record from coat pockets, car mounts and lecture halls with the screen dimmed.
Size: 88 pt beat 64 pt by 31% fewer missed taps.
Position: bottom centre, one thumb-width above the edge.
Feedback: one firm haptic tick on start, two soft ones on stop.
People did not want a bigger button. They wanted a button that was always in the same place.
The tape counter starts the instant you touch the button, before the screen finishes animating, so you know it is recording even if you are not looking.