FM Synthesis

General

– Very Different from Subtractive Synthesis as with FM Synthesis we actually Growing a Sound by Creating Partials / Overtones from the Ground Up (Instead Subtracting)

– FM Synthesis has Operators that are Pre-Stacked in different Ways

– the Principle is any of the Pre-Stacked Forms is based on a specific Carrier as the Basic Sound Source, then you Modulate that Carrier with a next Carrier (for Example B) by a certain Ratio and so on with a 3rd Carrier C that affects B and down to A etc.

– very Simple said, 1 Oscillators Waveform is Modulating another Oscillators Frequency

– it is also called “Carrier to Modulator Ratio”, where the Carrier in a Frequency Modulation Setup is the Audio Signal that gets Manipulated (the same goes for Vocoding, Ring Modulation)

– so for Example if you Change the Ratio of A in a A /B Setup, B is the Carrier and A is the Modulator (simply Memorise Modulator = the Source that currently Changes Ratio)

– if we use Ratios that are Integers, that is Whole Numbers (i.e. all Zeros to the Right of the Decimal Point), we get Even Harmonics which are Inline with the Harmonic Series 

– so if we use Non-Integer Ratios we get Detuned Results (Closer to more Organic Material)

– also good for Bright and Harsh Sounds, Bell Sounds, Marimba, Basses

– FM should also be Familiar as we all know  from the Term “FM Radio”

How FM Radio Works 

1) a Radio Wave is Broadcasted at a Specific Frequency (e.g. 91.6 Mhz) 

– this is Called the Carrier Wave

2) an Audio Signal, let’s say a Human Voice is then used to Modulate the Frequency of the Carrier Wave

3) Finally the Receiver that is receiving that Signal is Tuned to the Proper Carrier Frequency

–  it Detects the Changes in Frequency of the Carrier Signal and Amplifies it

– that’s how we get FM Radio

John Chowing

– Yamaha made FM Synthesis Popular with their DX 7 and DX 9 Synths, but before was Don Buchlar Popped FM in a Synth first and John Chowing Created different Algorithms

– this Guy Experimented with a Sine Wave Carrier and Modulated the Sine Wave Carrier with another Sine Wave with the same Frequency Range

– the Result was a Sound with Rich Harmonics Sine Wave

– these Harmonics are Called “Side-Bands” and can be Shifted around by Altering the Pitch of the Modulator Wave

– this Created a Simple, Inexpensive and Predictable Way to get Interesting Sounds from a very simply Source

– her Evolved Algorithms that use Multiple Sine Waves Modulating each other in a Variety of Waves

– these Algorithms simply used more than 1 Sine Wave OSC and each OSC can be used as either a Modulator or as Carrier

–  this Patent was then Licensed by Yamaha and the DX7 Synth was the Result