Introduction to synthesis Flashcards
What are the three stages of a typical synth?
Oscillator, Filter, Amplifier
Describe the Oscillator.
Signal Generator (creates the wave – sine, saw, etc.)
Describe the Filter.
Change Frequency Content (LPF, HPF, BPF, Slope, Resonance, etc.)
Describe the Amplifier.
Change Amplitude (i.e. varied over time – envelopes, etc.)
As well as signal generators, what can oscillators be used as?
Signal modulators – used to control a variable (e.g. low-frequency oscillators, or LFOs)
How can oscillators be combined?
- Additive synthesis adds sine waves together (as harmonics or partials) to build up complex tones.
- Subtractive synthesis uses complex tones to generate many harmonics, which are then filtered.
How do analogue synths add richness to a synth voice?
Combining several types of wave together.
Describe the audio signal and LFO of a sine wave.
Audio signal = pure, flute like
LFO = gentle, and/or gradual change
Describe the audio signal and LFO of a sawtooth wave.
Audio signal = buzzy, nasal quality
LFO = falling attack (rising reverse-attack) shapes
Describe the audio signal and LFO of a pulse/square wave.
Audio signal = square: hollow, clarinet-like, sometimes buzzy. pulse: varies from hollow to thin.
LFO = alternates between two states (a high value and a low value) - also useful as trigger signals.
Describe the audio signal and LFO of a triangle wave.
Audio signal = hollow like a square wave but less bright
LFO = Gentle and/or gradual change but sharper changes than sine at maximum and minimum
Describe the audio signal and LFO of noise.
Audio signal = ‘sss’ sound (white noise), ‘shh’ sound (pink noise).
LFO = random variations of a setting.
What do filters modify?
Filters modify the frequency characteristic of a input signal – adding to, or taking away from, a range of frequencies within the overall sound
What are filters the basis of?
Subtractive synthesis
What does the cutoff frequency in a LPF and HPF define?
What ‘high’ and ‘low’ frequencies are filtered. The cutoff is defined as where the amplitude has fallen by 3dB.
What are shelving filters used to alter?
- High and low shelving filters used to alter high and low frequencies respectively
- They either boost or cut some of the signal
(most “bass” and “treble” controls are of this type)
What do band pass filters allow?
Band-Pass Filters allow a band of frequencies through around a centre frequency (Fc)
What do band-stop filters stop?
Band-Stop (or Band Elimination, or Band Reject) Filters similarly remove a band of frequencies
What do peaking/notch filters do?
Peaking (or notch) filters boost (or cut) around a centre frequency, without cutting other frequencies.
The “sharpness” of the filter is defined by the Q factor. High values of Q are sharper.
How are amplifiers used in synthesisers?
In synthesisers, amplifiers are used to make a sound more interesting by varying amplitude over time.
What part of an oscillator does an LFO control?
Frequency (pitch) - (like Vibrato, where violinists rock the finger to waver pitch)
What part of a filter does an LFO control?
cutoff frequency - (like Wah-wah, on guitars or the human voice)
What part of an amplifier does an LFO control?
gain (like Tremolo, where woodwind players vary breath strength).
What do envelopes control?
They control the change of a parameter over time (e.g. amplitude, frequency, filter)
