DemoFrequency Player is a tone and frequency generator that runs in the browser. Play any frequency from 20 Hz to 20 kHz as a sine, triangle, square or sawtooth wave, and always see the musical note it is nearest and how many cents away it sits. Drag a dial of note names to tune by ear and flick it to glide, tap any of the 88 piano keys to jump to that note, type an exact value such as 440 or 2.5k, or nudge it with buttons that step by an octave, a semitone, 1 Hz or 0.1 Hz and repeat while held. A logarithmic slider sweeps the whole audible range, presets cover test tones like 60 Hz hum and 1 kHz, and the reference pitch for A4 is adjustable. Tones start, stop and retune without clicks. Works with mouse, keyboard and touch on phones and desktops. Built with React, TypeScript and the Web Audio API.