This is an interactive instrument called The Subtractive Synth Playground. You can use subtractive synthesis to experiment with what it does to a sound.
Just click the piano keys that appear on screen using your mouse to play the instrument, or if you prefer a more natural feel then try playing with your computer keyboard. The interface presents the sound spectrum so you can see in detail how your changes alter the tone.
How to Use The Subtractive Synth Playground
Begin with a key press. This is an octave from C to B on the keyboard. Accidental keys as well as natural ones is included. Alternatively, if you wish, you can use your computer keyboard where the white keys correspond to the keys from A to J. Black keys then correspond to the keys H, Y, T, E, W. You can press more than one key at once for playing chords. The resultant harmonics will be shown visually updated to include them all.
At the top of the instrument is the display of the harmonic spectrum. The dashed bars are the raw oscillator signal, and the solid bars represent what’s passing through the filter. By clicking on an individual bar, you’ll be able to hear just that harmonic by itself. This helps you understand the contribution each frequency make to the overall character of the sound.
Top left are the three choices of source waveform. The sawtooth wave is bright and contains all harmonics. The square wave sounds hollow and like a reed, but it contains only odd harmonics. The triangle wave sounds flute-like and soft with rapidly diminishing harmonics. These selections change the number of partials that the filter can then shapes into something else.
The filter reduces high frequencies by controlling the filter’s horizon. Use the cutoff slider to increase (raise) or decrease (lower) the frequency that is let through. Lowering the cut-off will remove the top harmonics and darken the sound. You can highlight the frequencies around the cut off by increasing the resonance. This brings in a bit of a whistling or nasal character to the tone.
Add some motion using the filter envelope. You can choose for the filter to open up slightly when you depress a note and allow more harmonics to pass. Then it closes again, settling on the sound. This is emulating the attack of an acoustic instrument such as a plucked string. The amount that the cutoff opens up in the attack phase is controlled by the filter lift slider. This modulates with the cutoff tide.
Activate a low frequency oscillator by toggling on the cutoff tide button. It will then modulate the cutoff frequency automatically. The result is a wah-wah effect. Use the tide depth slider to control how deep it goes and the tide speed slider to control how fast it goes.
To shape the volume, use the VCA flight path controls. These is like the ADSR controls that control how the sound acts when you press a key. The attack controls the length of time it takes for the volume to rise to its full value. The decay controls the rate at which it drops down to the sustain level. The sustain, as you’d guess, sets the volume during the duration that the key remains down. The release sets the length of time the sound fades once you let go.
You can adjust the pitch range by changing the register on your keyboard. For a low bass register, choose C3 B3. For a middle treble range, select C4 B4. This can be useful if you want to see how the filter behaves with different base notes. The spectrum display will update with the harmonics of the new root note.
Preset patches are loaded easily via the spectral constellations. Every button has a full complement of envelope, filter, and oscillator settings. Bass is a solid low end from the sunlit saw patch. A percussive hit with a sharp attack comes from the ringing pluck comet. You can do much more with these presets and the available controls.
The Subtraction Macro is a slider (cloud cover) that changes from one extreme to another. It changes the cut off frequency as well as the resonance at the same time. If you drag to the left, the filter opens up making the resonance lower and the sound bright and not filtered at all. If you drag right, the filter will close down increasing the resonance for a tight focused tone.
The fullscreen button expands the workspace by removing the surrounding content on the page to give you more room to easily access controls within the interface. To get out of fullscreen, just click the fullscreen button again. Alternatively, use your browser’s default keyboard shortcut(s) to get out of it as well.
Clicking the how to play button will open up a help panel, which details the nitty gritty of each part. If you want to see what happens in real time, this might be for you because it describes how the app’s output relates to the visual spectrum.
Try out the Hero experiment button. This automatically sweeps through the filter cutoff, starting high and moving down. The button will show you how far the filter sweeps smoothly. Clicking on the button stops the sweep wherever you are.
Use the observatory level slider to adjust the master volume of the instrument. This means the amount of overall loudness that comes out. Don’t be afraid to keep this at a comfortable level as you use high levels of resonance. Otherwise, you’ll get a loud peak suddenly.
The notes on the keyboard can be moved around using the arrow keys on the computer keyboard. It’s useful when working with the keyboard and not wanting to stretch to the mouse. The note that has the focus will sound when you press either the space or the enter key. This is useful if you’re typing out a melody precisely.
Observe that the bar colors and heights in the spectrum change. The solid bars indicate what sound is actually being sent to your speakers. The dashed bars are the potential energy coming from the oscillator that the filter filters out. You can see it visually. When lowering the cutoff, watch the bars go away to get feedback about subtraction.
A low sustain level and slow attack create a percussive pluck sound. The attack was very fast. It decays quickly. It hits hard and fades away quickly. It is like a marimba or a plucked string.
A vocoder increases resonance and lowers the cutoff. The filter now draws attention to the narrow band of frequencies it’s passing through. This, coupled with the modulation of the cutoff on the tides, gives you that robotic sweep of a vocoder.
Drag the cutoff slider down, playing a chord as it does so slowly. Observe how the overtones fall away first on the high end of the spectrum. What happens to the sound? From complex, bright tones, we hear simple, dark sounds. This demonstrates the core of subtractive synthesis in action.
When there are too many notes down, use the silence button to get rid of them all. Otherwise, your mix gets cluttered. It gives you a clean slate from which to begin again and try another experiment or patch.
Choose a waveform, press a key, and go. Twiddle the filter cutoff until it sounds good. Shape the length of the note by tweaking the envelope. Check out the preset constellations for various combinations that produce unique timbres. Explore the parameters; let your eyes help your ears.