Synthesis.

(This blog post consists of notes taken from my synthesis lecture, as prior to this class I was only aware of small aspects of synthesis, and so I thought it was best to create a blog post documenting the key parts.)

Synthesis is the process of creating sound electronically, synthesisers generate sound waves using electrical signals, which are then shaped and manipulated to produce a wide range of tones and textures.

There are several major types of synthesis, some include:

• Subtractive (Removing frequencies using filters.)
• Additive (Sounds are created by layering multiple sine waves.)
• FM– Frequency Modulation (One waveform modulates the frequency of another.)
• Wavetable (Waveforms are digitally manipulated to create a wide range of sounds.)
• Granular (Divides sample up into tiny grains that can then be played back at different speeds, in different frequencies.)

FM Synthesis-

• A technique where the frequency of one waveform (the carrier) is modulated by another (the modulator).
• John Chowning, a composer and researcher at Stanford University, invented FM synthesis in the 1960s.
• You can multiple modulators with fm synthesis.
• Consists of multiple oscillator that you can change individually and each one affects the other, with the carrier being the final outcome.
• Yamaha DX7 is the most famous FM synth.
• Fm synth allowed a much broader range of sounds and really made a change in digital music production in the 1980s.

Synthesised sounds begin as audio signals generated by oscillators, as signals pass through the components of a synth, the basic waveforms are shaped and sculpted by filters and envelopes. Sound wave forms include;

• Sine wave
• Square wave 
• Sawtooth wave 
• Triangle wave 

Amplitude envelope – An envelope is a path through which a sound will pass, determining the length of the sound. -It determines how there sound will evolve.

ADSR-

• Attack= Amount of time it takes for sound to come in.
• Decay= Amount of time it takes to reach the next level of volume/ the decay level.
• Sustain= The sustain level is volume based, the second point in the envelope is the sustain level.
• Release = How long it takes to die away after releasing finger of the key.

More than one note at the same time= Polyphonic

One note played= Monophonic

Filters-

• Low pass filter- Removes high end frequencies. You have a cut off point for the sound, the point at which the cut of is made can be emphasised by moving it up and down- changing the cut off point- this is called the resonance, however in EQ this is called the Q (it describes how narrow or wide a filter is around a certain frequency). Depending on the db number, the filter can be more or less efficient, 12db is most common.
• High pass filter- Removes low end frequencies.
• Band pass- Allowing you to preserve a certain range, removes sound from the left and right of the cut of point.
• Notch filter- Creates a notch (a dip) so the sound at that range is removed and the sounds from the left and right remain.

Modulation-

• Modulation involves changing parameters over time.
• LFO- Low frequency oscillator, an interaction between the sound waves- commonly used for tremolo or vibrato. The LFO has its own waveform. Used to influence change in volume or pitch.
• VIBRATO= varying pitch
• TREMOLO= varying volume
• Glide control- A pitch bend, the sound will guide from one pitch to the other, the dial on the synth controls the time taken to reach the second note.