Metronome

The metronome takes a real time signature instead of a beats-per-bar count, which means compound meters are counted the way musicians count them: 6/8 is two dotted-quarter beats, not six eighths. It has tap tempo, an accented downbeat, and subdivisions drawn as actual beamed notes where the single note you're hearing lights up. There's also a latency slider for a Bluetooth speaker or a classroom projector — it delays the picture, never the click, so the beat itself stays exact.