Sound Synthesis

Additive synthesis

• additive synthesis: creating sound by adding harmonics in the sound
• achieved by stacking Oscillators together; mostly using sine waves
• each harmonic added changes the waveform
• 🕹️ Ableton's Operator uses a bar chart, with each bar representing the harmonic series and the height corresponding to that harmonic's volume
  • 🕹️ In Serum, the second row of bars offsets the phase of the first harmonic
• harmonic every two → square; harmonic every bar → sawtooth

Interesting

You control each harmonic independently, letting you shape sounds with more flexibility.

Tip

Importing a waveform (or sound source) in loads its harmonic content, which can be useful to observe how the sounds are formed from a additive synthesis perspective.

Subtractive synthesis

• subtractive synthesis: starting with a sound rich in harmonic content, then gradually removing some of that content using filters
  • e.g. lo-pass filter cuts the high end → sound is less harsh and more muffled; vice versa
  • a hi-pass filter is useful to make space for other sounds in the mix
• in its purest form, you can use white noise
  • the cutoff filter follows which key you press on a keyboard → letting you play notes

Wavetable synthesis

• Serum or Ableton
• oscillator → wavetable containing several waveforms
  • knob lets you cycle through all and morph sound → adds motion, makes it more organic
• varying waveform together with opening filter or drive of distortion → comes alive
  • any waveform can morph to any waveform → endless possibilities
• you can draw your own waveforms, or import samples to extract waveforms from
  • you can interpolate between waveforms to move between them smoothly
  • 🕹️ in Serum, 'morph section'

Amplitude modulation (AM) synthesis

• amplitude: volume of the sound
• amplitude modulation: volume changes following another signal
• you need 2 oscillators – carrier and modulator
  • carrier: sound source
  • modulator: controlling the volume knob
• LFO: low-frequency oscillator; provides a very slow (low) sine wave
• modulators that move fast enough distort the shape of the waveform → begins adding harmonic content to original signal
  • essentially stopping and starting very fast → creating low grit underneath the original sine wave
• changing amplitude changes the overall volume of added harmonics
• you can experiment with changing the Types of waveforms the carrier & modulator use
• ring modulator: makes a sound more metallic; only added harmonics remain and original carrier frequency disappears
  • originates from the 4 diodes linked together in analog