Instruments

Free online subtractive synth

This is a free online synthesizer, and it is a subtractive one, which is the family almost every classic synth belongs to. You start with a waveform that is deliberately rich in harmonics, then take frequencies away with a filter until what is left is the sound you wanted. Play it with the ZXCVBNM and ASDFGHJK rows of your keyboard, or tap the keys on screen. Four blocks of controls do everything: the oscillator picks the raw waveform, the filter decides what survives, the envelope shapes how the sound starts and stops, and the LFO moves a control for you while you play.

Try it

Play a note and let it ring. Click the keys or use your computer keyboard: ZXCVBNM for the lower octave, ASDFGHJK for the upper one. – and + change octave.
Without touching anything else, cycle the waveforms on the same note: Sawtooth, Square, Triangle, Sine. Listen to the brightness drain away.
Go back to Sawtooth. Close Cutoff almost all the way, then open it again slowly. This is the move the whole name is built on.
Push Reso above 10 and walk the Cutoff again. A whistle appears and follows the cutoff point, and that is where the acid sound lives.
Switch the filter type from Lowpass to Highpass without touching Cutoff. Same note, same number, opposite result.
Take Sustain to zero with Decay halfway, then hold a note without letting go: it dies on its own while your finger is still down. Put Sustain back to 100% and the same note holds until you release.
Set the LFO to Cutoff, Rate near 0.5 Hz and Amount halfway. Hold a long note and do nothing else.

What to listen for

The waveform decides what material you are working with. A sawtooth carries every harmonic, which is why it starts almost every bass and lead ever made. A square drops the even harmonics and sounds hollow because of it. A triangle and a sine carry almost no harmonics at all. Run step 2 again with the Cutoff low: the same filter does a lot to the sawtooth and almost nothing to the sine. That is not a shortcoming of the tool, it is the reason you choose the waveform first and the filter second, because a filter can only remove what is already there.

The LFO is an automatic hand on a knob. On Cutoff it gives you the breathing filter from step 6, on Pitch with a low Amount it gives vibrato, on Volume it gives tremolo, and the same speed that sounds musical on one destination sounds twitchy on another: try 0.5 Hz and 6 Hz on all three. Sub is a second oscillator an octave down, and it is what separates a bass you can hear on a phone from one that only exists on big speakers. The envelope has all four stages: Attack and Decay draw what happens when you press, Sustain is the level the sound holds while you keep the key down, and Release is what is left after you let go. Step 6 is what separates Sustain from the other three, because it is the only stage a short note never reveals. With Attack at 1 second and Release at 2, the same note stops being struck and turns into a pad. With a MIDI keyboard connected and a browser that supports Web MIDI, Connect MIDI lets you play it from the keyboard, with velocity, and the mod wheel is wired to the LFO Amount.

Questions

What does subtractive synthesis actually mean?

It means you begin with more harmonic content than you need and remove what you do not want. A sawtooth contains every harmonic; a filter takes the top off it. What you remove is what makes the sound yours.

What is cutoff and what is resonance?

Cutoff is the frequency where the filter starts removing content. Resonance boosts the frequencies right at that point, which is what produces the whistle you hear when you push it up. Sweep the cutoff slowly with resonance high and you will hear both at once.

Why does the same note sound like a different instrument when I change the envelope?

Because attack, decay, sustain and release control how the sound behaves over time, and time is most of what your ear uses to identify an instrument. A slow attack turns a pluck into a pad without changing a single note.

Does it work on a phone?

Yes. On a phone you play the on-screen keys instead of the computer keyboard, and the layout adapts to the smaller screen.

This tool is one part of the picture. Electronic Music Production for Beginners covers the rest.