Post on 04-Jan-2016
Subtractive Synthesis
• Involves subtracting frequency components from a complex tone to produce a desired sound
• Why is it not worth trying to subtract frequencies from a sine wave?
• A sine wave only contains one frequency
Subtractive Synthesis
• Unwanted frequencies are attenuated using filters
• The most basic subtractive synth needs at least one oscillator and one filter
Subtractive Synthesisers
• Subtractive synths provide:
• two or more oscillators
• a noise generator
• at least one filter
• at least one envelope
• an LFO
• a modulation matrix
Filters
• Used to attenuate spectral components
• Implemented using electronic components or a digital algorithm
Low Pass Filter
Amp.
Cut-off frequency
Frequency
• Lets through everything below a certain frequency
Filter Slope
• Ideal filters are like brick walls
• All real filters have slopes
• So some sound gets through beyond the cut-off
Envelopes
• Determine how the value of a certain parameter of a sound changes over time
• Can be used to alter any parameter, e.g. pitch
Amplitude Envelopes
• How the amplitude varies over time affects the character of a sound significantly
• So most synthesisers have an amplitude envelope
Amplitude Env. Parameters• attack – occurs at the start of the wave and is the
time it takes for the sound to reach peak amplitude
• decay – the time it takes for the peak amplitude to fall back (possibly to zero)
• sustain – the amplitude level the sound will fall back to following the initial decay
• release – the amount of time it takes for the sound to fall back (or decay) to zero after the sustain period (or after the key is released)
Modulation
• Modulation traditionally means to change the key of a piece of music
• With synths it means to alter a parameter (target) in accordance with another signal (source)
• Example targets: amplitude, pitch, cut-off
Modulation
• Example sources: envelope, LFO, velocity
• Alter the intensity of the modulation over time
• Slider often used to alter the max extent of the modulation (the intensity of the overall effect)
Hardwired Modulations
• The ESP allows the LFO to be applied to:
• frequency (pitch) of oscillators; or
• the cut-off frequency
Modulation Matrix
• Target: parameter to be altered
• Source: signal that is used to alter target
• Slider: sets modulation intensity
• Via: varies modulation intensity by another parameter