Overtones Generator: Learn How Harmonics Build a Timbre

Overtones are usually explained with a single frozen frequency graph, which is a strange way to teach something you're supposed to hear. This overtones generator synthesizes the notes of an A major guitar chord using additive synthesis: each note is built by summing harmonics whose individual weight you can control, letting you hear how the timbre changes as you shape it.

The time-domain and frequency-domain views track every change you make, so you can connect what you're hearing with what's actually happening to the harmonic series — a hands-on way to understand what overtones are, not just a definition to memorize. Part of AudioFxLab's free collection of interactive audio tools.

Parameter Guide: How Each Control Works

Oscillator Power (ON/OFF)

Each of the six oscillators can be switched on or off independently. Turning several on at once lets you hear and see how multiple tones combine, both in the time-domain waveform, where their sum creates complex, non-sinusoidal shapes, and in the frequency-domain display, where each oscillator's fundamental and harmonics appear as separate peaks.

Where to start: begin with a single oscillator active to understand how one fundamental plus its harmonics builds a timbre, then bring in a second to hear how two pitches and their overtone series interact and combine in the frequency spectrum.

Frequency (Hz)

This sets the fundamental frequency of the oscillator — the lowest, and usually loudest, component of the tone, and the one that determines its perceived pitch. Every harmonic generated by this oscillator sits at an integer multiple of this frequency (2x, 3x, 4x, and so on), which is what defines a harmonic series as opposed to an arbitrary set of frequencies.

Where to start: the six oscillators default to the notes of an A major chord, so you can already hear how frequency relationships between multiple fundamentals interact; try changing one to a non-harmonically-related frequency to hear the difference between a consonant and a dissonant combination.

Overtones (count)

This sets how many harmonics above the fundamental the oscillator generates — not their individual loudness, which is controlled by dragging on the frequency-domain display, just how many of them exist at all. A low count produces a simpler, purer tone closer to a single sine wave; a high count adds many more harmonics into the mix, which is one of the main ingredients that make a timbre sound rich or "buzzy" rather than plain.

Where to start: try a low count (2-4) to hear something close to a pure tone, then increase it toward 64 to hear how the added harmonic content changes the character of the sound, especially when combined with the Random Timbre button, which assigns each harmonic a different, decaying amplitude.

Fundamental / Overtones toggles

These two buttons let you isolate what you're hearing, and seeing, from a single oscillator: Fundamental toggles the base frequency itself on or off, Overtones toggles the entire harmonic series on or off, independently of each other. Turning off the fundamental while keeping overtones active is a useful way to hear, and see on the frequency display, exactly what the harmonics alone sound like, without the pitch-defining fundamental underneath them.

Where to start: switch off Overtones first to hear the fundamental alone, a pure sine tone, then switch it back on and Fundamental off to hear the harmonics in isolation — the contrast makes it clear how much of a complex tone's character comes from the overtones rather than the base pitch.

Harmonic amplitude (drag on the frequency display)

Every individual harmonic bar on the frequency-domain display can be dragged up or down to set its amplitude relative to the others. This is the most direct, hands-on way to shape a timbre in additive synthesis: rather than choosing a preset waveform, you're deciding, harmonic by harmonic, exactly how loud each component of the sound is — which is, in principle, exactly how any real-world timbre could be described and reconstructed.

Where to start: try shaping a harmonic series so it emphasizes only the odd harmonics (1st, 3rd, 5th...) and mute the even ones — that's the basic recipe behind a clarinet-like or square-wave-like timbre — then compare it with a series that includes all harmonics evenly.

Master Volume

A simple overall level control for the audio output, independent of the additive synthesis parameters — it doesn't change the timbre or the relationships between harmonics, only how loud the result is when played back.