Online Tone Generator
Pure test tones 20 Hz–20 kHz, three-voice intervals, sweeps and ear training.
Listen safely. Volume starts at 25 % on purpose. Turn your system volume down before you press Play, then raise it slowly. Sustained tones — especially square and sawtooth, and anything above about 4 kHz — are fatiguing and can damage hearing at high levels. Never wear headphones at full output while sweeping the frequency slider. Adding tone B and tone C makes the sound denser, so drop the master volume before you stack voices.
The main tone
- Big slider — drag to sweep frequency. The scale is logarithmic, so each equal step of travel is an equal musical interval.
- Hz field — type an exact frequency (20–20000) and press Enter or click away.
- −10 / −1 / +1 / +10 Hz — fine nudge buttons for beating and tuning work.
- ÷2 / ×2 — jump down or up one octave. Snap pulls the frequency onto the nearest equal-tempered note.
- Waveform buttons — sine, square, sawtooth, triangle. The selection applies to every voice and is drawn live in the scope.
- Play tone / Hold — Play toggles the sound on and off. Switch the Hold button on and the transport becomes press-and-hold instead: sound only lasts while the button (or Space) is held down, which is the mute-safe way to audition loud or high tones.
One-octave keyboard
- Twelve full-size keys, all visible at once — nothing scrolls. Press and hold a key to sound it; release to stop. If the tone is already playing, a key retunes it instead.
- ◀ / ▶ octave shifts the whole keyboard and the current pitch by one octave (C1–C8). The keyboard always shows the octave your current frequency lives in, and the nearest note is lit.
- Tab to a key and press Enter for a short blip if you are using a keyboard rather than a pointer.
Intervals: tone B and tone C
- Turn on Tone B (or C) to sound a second and third oscillator alongside the main tone. Each has its own frequency field, −1/+1 Hz nudges and level.
- Ratio presets set the voice to an exact whole-number ratio of the main tone: 1:1 unison, 6:5 minor third, 5:4 major third, 4:3 fourth, 7:5 tritone, 3:2 fifth, 5:3 major sixth, 2:1 octave. Just ratios are used, so a preset interval is genuinely beat-free.
- The readout under each voice names the nearest simple ratio, how many cents you are away from it, and how consonant that ratio is.
- Beat rate appears whenever the two tones are close enough to beat. It is the difference between the coinciding harmonics, beats = |p · fA − q · fB| for the ratio p:q — for a unison that is simply |fA − fB|. Zero beats means the interval is exactly in tune. The +3 Hz beat button on tone C sets up a 3-per-second wobble instantly.
- The scope draws each voice faintly and the summed waveform in bold, so you can watch the interference envelope swell and cancel at the beat rate.
Sweep
- Set a target frequency and a duration, then press Sweep. The main tone glides logarithmically from where it is now to the target, so the pitch rises at a constant musical rate.
- When a sweep lands, the target flips back to where the sweep began, so pressing Sweep again runs the same span in reverse. Swap ends exchanges the current frequency and the target by hand. Press Sweep while it is running to stop it where it is.
- Turning on Tone B or Tone C starts the sound if it was stopped, so a ratio preset is always audible in one press.
Tone shape
- Attack and Release (3–600 ms, default 15 ms) set how fast the note fades in and out. Short values give a clinical click-free test tone; longer values give a soft swell.
- Tremolo modulates loudness, Vibrato modulates pitch (in cents), and Modulation rate is the shared speed of both, 0.1–12 Hz. Both start at zero, so the tone is a pure sine until you ask for otherwise.
Ear training
- Match the pitch. A hidden target is drawn inside a stated window. Press Hear target, then move the big frequency slider until your tone matches, comparing with Hear guess. Submit scores you in cents and in Hz. Bands: Wide ±600 cents (a full octave of hunting room), Medium ±250 cents, Narrow ±75 cents.
- Round score is 100 · (1 − error / band), rounded, floored at zero. Landing inside a fifth of the band counts as a hit and extends your streak; missing resets it. Rounds, streak, best streak, best error and total score are kept for the session only — nothing is stored.
- Higher or lower? Two tones play in sequence and you say whether the second was higher or lower. It is adaptive: every correct answer shrinks the step by 30 %, every miss widens it by 60 %, from 400 cents down to 3 cents. Your best is the smallest step you have called correctly.
Keyboard shortcuts
- Space start / stop the tone (hold it down when Hold mode is on).
- ← → nudge −1 / +1 Hz · ↓ ↑ nudge −10 / +10 Hz.
- [ ] octave down / up · N snap to nearest note · R reset everything.
- 1–4 select sine, square, sawtooth, triangle.
- B C toggle tone B and tone C · S start / stop the sweep · G new ear-training round.
- These shortcuts are ignored while a slider or a number field has focus, so the native slider and typing behaviour still work. Click the widget background first to use them.
Conventions and formulas
- Tuning is 12-tone equal temperament with an adjustable A4 reference (default 440 Hz), C4 = middle C, MIDI 60 = C4, MIDI 69 = A4.
- MIDI number from frequency: n = 69 + 12 · log₂(f / A4).
- Frequency from MIDI number: f = A4 · 2^((n − 69) / 12).
- Deviation: cents = 1200 · log₂(f / fnearest), shown against the nearest note, range ±50 cents.
- At A4 = 440 Hz: A4 = 440.000 Hz, C4 = 261.626 Hz, A#4/Bb4 = 466.164 Hz — all read ±0 cents.
- Square and sawtooth carry far more energy than a sine at the same peak, so a small fixed loudness trim is applied per waveform. The volume number is the sine-referenced level. Stacking voices divides the master by √n so three tones are not three times as loud.
Tips
- Tune an instrument by beats: set the target note with Snap, play a sine, and sound your string against it. The slow "wobble" you hear is the beat rate — it equals the difference in Hz. Zero beats means you are in tune.
- Hear why a fifth sounds "clean": turn on tone B, press the 3:2 preset, then nudge B by +1 Hz. The interval stays a fifth but starts to churn — that churn is exactly what a piano tuner listens for.
- Find your high-frequency limit: set a 5-second sweep from 8000 to 20000 Hz at low volume in Hold mode and note where the tone vanishes.
440.0 Hz = A4, +0 cents
Frequency MIDI 69
Snap moves to the nearest equal-tempered pitch (0 cents).
Waveform Sine
Keyboard C4 – B4
Press and hold a key to sound it. All twelve keys are on screen — the octave buttons move the keyboard and the pitch together.
Intervals & multi-tone 1 voice
Off.
Off.
Presets use whole-number (just) ratios of the main tone, so a preset interval beats at exactly 0 Hz. Nudge by 1 Hz to hear it start to churn.
Sweep 440 → 880 Hz
Glides the main tone logarithmically from where it is now to the target. When it lands, the target flips back to the start so the next press sweeps the same span in reverse.
Tone shape
Output
The A4 reference re-maps note names; it does not change the tone you hear.
Nearest note 440.000 Hz
The exact equal-tempered frequency of the nearest note at the current A4 reference. Your tone is 0.000 Hz from it.
Semitone steps snap first, then move by one equal-tempered step.
Ear training 0 points
Pick a band and press New round. A hidden tone is drawn inside the stated window; move the big slider until you match it.
Press New pair. Two tones play in a row — say whether the second one was higher or lower. It gets harder every time you are right.
It is a precise interval/frequency explorer that you can click on to play. There are sliders and a virtual keyboard as well for playing around. To be able to play it quickly, you can also use your computer keyboard. No setup necessary; just open in your browser.
A single octave of keys is displayed on the virtual keyboard. Just click on a key (black or white) to hear a tone at the selected pitch. The octave shift buttons (labeled with note names/arrow symbols) allows you to move the entire keyboard up and down. Below the keyboard is the frequency slider for continuous fine-tuning of pitch. Alternatively, enter an exact frequency into the text input field to have it play back.
How to Use the Sound Explorer
Alternatively you can easily alter the pitch using your computer’s keyboard. To step the pitch up or down by 10 hertz use the up/down arrow keys. To make the change in smaller steps of one hertz use the left/right arrow keys. The bracket keys will alter the pitch by an octave either side. The n key will reset current frequency to the next closest equal-tempered note. The spacebar begins and ends the tone.
The waveform selector changes the type of sound. Pure, soft tones come from sine, whereas square creates a reedy, hollow sound. The sawtooth is buzzy and bright, while triangle option provides a softer version of the square wave. It lets you hear the impact of various harmonics on the texture of the pitch.
To control the loudness of what is produced there are volume controls. The first is a master volume slider that controls overall loudness of all the voices. If you want to add extra voices then you have the option to switch on voices B & C that will be able to produce a chord or interval. Each of these voices also has its own volume slider along with an input for frequency. This means you can mix sounds together as desired.
There are also shape controls that change the attack and release times. Shorter lengths mean the sound will begin and end quickly and longer ones gives you a more smooth swell.
Movement is added in the form of tremolo and vibrato. Vibrato modulates the pitch; tremolo modulates the volume. Each has its own slider to control depth of effect. The rate slider controls speed of the modulation. These allow you to experiment with how modulation changes tone and pitch perception.
Sweep: This automatically changes the frequency over time. Click on sweep after setting the target frequency/duration. It then glides the tone from its current pitch to the one you have set. It is useful if you want to hear a large interval or check the resonance frequency without having to adjust manually.
There are two ear training games where you can practice matching pitch. In one game you have to guess the hidden target frequency. Adjust the main slider as you go until you feel like it’s the same pitch as what you’re hearing, then submit your answer. In the other game they play you two tones and you have to say if the second tone is higher or lower than the first. Your accuracy determines difficulty of the next round.
With the hold mode engaged, the play button functions differently. With hold mode disabled, pressing play will turn the tone on or off. In hold mode, press and hold the play button to produce a tone. Hold mode prevents tone from playing indefinitely if you forget to stop it. Pressing the space bar while in hold mode will also sustain the tone.
Resetting all settings to default is done by pressing the r key. It brings back the frequency (to 440 hertz), disables additional voices and resets all the sliders. The help button will open up a help panel with more specific instructions. The fullscreen button takes the widget full-screen making it use more of your screen space, giving you a bigger canvas on which to display the waveform.
The other voices can be used to look into effect of dissonance and consonance. For example, set one of the other voices (say B) to a value that produces a simple ratio relative to the fundamental. A is 100 Hz, then make B 150 Hz (a perfect fifth). You’ll notice how the waveform combines. Each voice appears in pale color, while the combined form appear in bold. This kind of visual feedback will aid your understanding of how complex waveforms are made of simpler components.
Experiment with variations in attack and release time and observe their impact on the transient response. The longer the attack, the more difficult it is to fine tune your pitch; a short release will make the end of the note clear and distinct. Here’s where you play around with the envelope shape and its effect on the clarity of a tone.
In terms of feedback, the ear training games give instant results as to how accurately you are playing. I suggest starting with bigger intervals in either the upper or lower game to build your confidence. Then as your skills increase, you will gradually move to smaller differences between pitches. It’s an effective way of slowly tuning up your ear for pitch.
For more accurate experimentation, you can add in your own frequency value here via the input. If you’re trying out different intervals, this will be useful. Alternatively, you can quickly run through a sweep of frequencies using the slider. Between the sliding and precise input options, you have complete control of the pitch.
Listen to how each of these modulations affects the sound. A touch of vibrato can bring life into what would otherwise be a still tone. Heavy tremolo can obscure the pitch entirely. Experiment with the depth and rate until you get the right mix for your experiments. You can use them to replicate the characteristics of an instrument, or even create a new acoustic environment around it.
This is a practice tool/widget. Spend some time getting to know it. Get to know all the controls. Try out various modulation/waveform/intervals. Find that every one makes a contribution towards the sound of this instrument. Begin playing today; see what you can make.