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Subtractive Sound Synthesis. 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.
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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
Filter Types • Low Pass Filters • High Pass Filters • Band Stop Filters • Band Pass Filters
Cut-off frequency Amp. Frequency Low Pass Filter • 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
Filter Slope roll-off dB 500 8000 KHz A low pass filter with a gentle slope of 6dB per octave.
Cut-off frequency Amp. Frequency High Pass Filter
Centre frequency Amp. Frequency Band Pass Filter
Centre frequency Amp. Frequency Band Stop Filter
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
attack decay sustain release amplitude time
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)
TS404 AMP ENV Subtractor AMP ENV
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
L.F.O. • Low Frequency Oscillator • 0.1 – 20Hz • Can be synched to the project tempo
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