Every sound is a sum of sine waves. Draw them, play them, watch them turn as circles on circles, and turn them into a lush pad.
Each bar is one sine wave. Drag across the bars to draw their levels, or focus a bar and use the arrow keys (1 dB per step).
Numbers under the bars: each partial’s frequency as a multiple of the note. The scale runs from 0 dB at the top to -48 dB.
Or play C4 to C5 on the keys below or on your computer keyboard: A S D F G H J K, with W E T Y U for the black keys.
Each partial is a circle as large as its level, turning as fast as its frequency and riding on the previous circle. The height of the last point, drawn over time on the right, is exactly the waveform you hear.
Turns your partials into a lush, seamless pad: each partial is smeared into a narrow band of frequencies with random phases (Nasca Octavian Paul’s PADsynth algorithm), so it sounds like a choir of slightly detuned copies.
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Start from a sine, saw, square, triangle, organ or bell, then drag the 16 bars to set how loud each sine wave is. Stretch the ratios to hear harmonic tones turn metallic.
Hold a note or play with your mouse, touch or computer keyboard. Circles on circles, the waveform and the spectrum all redraw from the same partials you hear.
Generate a PADsynth pad from your partials, set its bandwidth, loop it, and download the WAV for any sampler or DAW.
Additive synthesis builds a sound by adding sine waves together. Each sine is a partial: it has a frequency, usually a whole-number multiple of the note (the harmonics), and a level. Fourier showed that any repeating waveform can be written this way, so a saw is every harmonic at 1/k, a square only the odd ones, and a triangle the odd ones at 1/k².
The circles-on-circles picture is the same idea drawn as motion. Every partial is a circle that turns at its own speed while riding on the previous one. The height of the last point is the sum of all the sines, which is why its trace is exactly the waveform. Make one circle larger and you hear that harmonic get louder.
Real instruments are rarely perfectly harmonic. Piano strings are stiff, so their upper partials run slightly sharp; bells and bars have partials at ratios like 2.76 and 5.4. Moving the ratios away from whole numbers is what makes a tone sound metallic. And in most acoustic sounds the high partials die away first, which is what the Pluck switch imitates.
PADsynth, by Nasca Octavian Paul, takes additive synthesis one step further: instead of one exact frequency per partial, it spreads each partial into a narrow band of frequencies with random phases and computes the whole sound with one inverse FFT. The result is a long loop with no audible seam that sounds like an ensemble, ideal for pads and choirs.
One of the sine waves a sound is made of. Partials at whole-number multiples of the note are called harmonics; partials in between are inharmonic and give bells and metal their sound.
At audio speed the fundamental turns hundreds of times per second, far too fast to see. The picture turns the fundamental once every four seconds and keeps every partial at its true ratio, so the shape is the same as in the sound.
It raises every ratio k to the power 1 + stretch. The fundamental stays put and higher partials move further from whole numbers: a little sounds like a piano string, more sounds like a bell or a gong. Negative values pull them flat.
An algorithm by Nasca Octavian Paul, released into the public domain and used in ZynAddSubFX. Each partial becomes a Gaussian band of frequencies with random phases, and one inverse FFT turns that spectrum into a long loop that repeats without a click. The bandwidth slider sets how wide the bands are.
No. The sound, the pictures and the pad are all computed in your browser, and the WAV is saved straight from it.
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