Barbershop quartet

A fixed quartet — bass, tenor, alto and soprano — one pulse. Drag any dot on any shape — they all share the same tempo and scale, so however you tune them, it still sounds like one quartet.

Click or tap a shape to select it, then use its buttons or the keyboard: numbers 3–9 set its vertex count, ←/→ rotate its phase. Space plays or pauses the whole quartet. Each part's Mute button silences that voice without breaking the shared beat.