BKS Harmonic is an additive synthesizer that builds sound from individual overtones, then gives you tools to shape, scan and filter them by harmony. Load it as an Audio Unit v3 inside AUM, GarageBand, Cubasis, Loopy Pro or any AUv3 host, or run it standalone. A TUNER THAT KNOWS ABOUT STRETCH Tune mode turns the scope into a tuner: it names the note it hears and shows how far sharp or flat it is in cents, with a ring that closes as you land on the pitch. It tunes against the stretch curve rather than equal temperament, so it follows a real instrument. Stretch shapes the overtones inside a note; Key Stretch makes the keyboard follow it, so octaves widen the way a piano's do. FOURTEEN TUNING SYSTEMS, AND A TEMPERAMENT EDITOR Equal and Just, five historical temperaments, and six from outside the European tradition including Maqam Rast, Turkish Rast, Slendro, Pelog and the Harmonic Series. The Temperament slider is a morph, not a switch: fully left is Just, fully right is whichever you chose. Twelve bars show any system as cents away from equal; drag one to make the tuning yours, then copy it out as plain text. Tunings save with the preset. FIVE HUNDRED SCALES Searchable by alternate name: malkauns, nikriz, bhupali and freygish find the right set. THE PARTIALS ARE THE INSTRUMENT The partials display shows every overtone in your sound, and four tools work on it directly. FOLD sweeps upper partials below the fundamental, redistributing energy across harmonic layers — not a filter. The OVERTONE SCAN steps a spotlight through individual partials with triangle, saw or random patterns, and can visit only partials in the active scale. The HARMONIC GATE reinforces partials whose pitch class matches your chord and suppresses the rest: capture a chord, follow MIDI, split the keyboard, or pick the notes on the gate's own keys. SCULPT draws the level and pan of every partial, slides the curve up the grid as a formant, and locks partials in place while the rest moves. THE HARMONIC VOCODER Pass live input or a sample through the synth as an effect. Your sound travels through a bank of tuned peaking bells rather than being replaced by filtered noise: open the Air and the source stays dry, tighten it and the bands resonate into it. Key Track is the mode switch: on it plays as an instrument, off it is a fixed filter you can sweep. Aimed at a sample, the bands track that sample's spectrum as it evolves. One level-matched Blend control crossfades it against the oscillators. PULSE-WIDTH MODULATION Set the core to a saw and Source 2 to a saw: the two ramps subtract, which is what a pulse wave is, and the phase between them sets the duty cycle. Modulate it and you have PWM. A preset in the Utility folder is ready to play. MODULATION A cog on almost every control, so the synth's own engine can drive nearly anything in the interface, including the display. Sources include velocity, envelopes, LFOs, how many notes you hold, how many oscillators sound, the synth's own output level, and Atmo, a shape driven by 84 years of barometric weather data from the Beat Kitchen Weather Sonification Project. Rates run from audio rate down to cycles that span years. THE SCOPE A stereoscope, oscilloscope, spectrum and a live per-partial display. Glow takes the trace from a hard line to a diffuse bloom, Colour sets the hue, Trace Speed and Dot set how it draws — and every one is a modulation target. Route velocity to Colour and the trace shifts as you play. LIVE INPUT A headphone button passes the side-chain straight to the output, so you can hear and see your input with nothing held: green when signal arrives, amber when a bus is connected but silent, red when nothing is. Resynth Speed locks a sample's playback speed to pitch, tape-style, or keeps them independent. Every control has a tooltip, presets work offline, and a harmony wheel follows what you play. One purchase, every update. Made by Beat Kitchen, a music production and teaching community.