Basic Sound Synthesis: Part 7 – Miscellaneous Stuff

Monophonic/Polyphonic: Early synthesizers were only capable of producing one note at a time, but through evolution of technology they became more and more powerful (and cheaper to produce), to the point that modern synthesizers can play a near-infinite amount of notes simultaneously (like a piano). However, most synthesizers still have the option of playing in a monophonic or polyphonic mode. Quite simply, a monophonic (think ‘mono’) synthesizer can only play one note at a time, and a polyphonic one can play two or more. The monophonic setting can be useful for some lead and bass sounds, as it prevents two keys from being held down accidentally and overlapping each other.

Portamento/Glide: Gives the ability to slide between notes. The effect of portamento is best used on monophonic sounds to create a bending between notes, but can also be used polyphonically when played in the style of block chords. The time (and occasionally scale) of the glide effect can be changed, allowing different severities of ‘bending’, from a simple glide, to a very slow sweep between adjacent notes (useful for SFX).

(Simple) FM: Although ‘frequency modulation’ is an entire form of synthesis itself, the basic concepts of its sound creation methods can also be used in subtractive synthesis. FM effects are produced in a similar fashion to a sped-up LFO, whereby the rate is set so fast that the oscillator produces an audible pitch. The resulting oscillator is then used to modulate the pitch of another oscillator, giving a generally non-harmonic sound, which is very sharp and biting. Due to the lack of pitch stability in analogue components, FM effects can not be reliably used on analogue synthesizer keyboards.

Oscillator Sync: The standard effect of oscillator sync (technically called ‘hard sync’ in this case), is the use of 2 oscillators – one which is the master, and the other the slave. The master oscillator runs as standard with its waveform, but the slave oscillator will be running faster or slower than the master. When the master oscillator is triggered, the slave oscillator will also start again through its waveform regardless of whether it has finished its cycle or not. Because the oscillators will be at different parts of the waveform cycle, strange harmonic effects are created when the two oscillators are triggered together.

Ring Modulation: One of the more well-known musical features from the past, ring modulation in music synthesis is the simple process of taking two oscillator inputs and multiplying them against each other depending on their frequencies. Because of the non-harmonic result, this is a good technique for creating dissonant, percussive sounds.

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