Once a movement's frequency is captured as a number, it can be mapped — frequency to pitch, amplitude to volume, period to rhythm — onto a piano, real or sampled.This is the project underneath Dancing Piano: using the exact physical quantities introduced today — the same ones that separate a hummingbird from an elephant — to let a tracked body play an instrument with its own motion.Every session from here builds, piece by piece, toward that pipeline: track, measure, map, sound.