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FM Synthesis by Adrian Frost

Part 1 - An Introduction "Frequency Modulation". Two words almost guaranteed to strike fear into the heart of any soft synth using musician. Frequency Modulation (FM) Synthesis has a reputation for producing harsh clanging discordant digital noises and bell sounds, lots and lots of bell sounds. Throw in talk of operators, carriers, modulators and ratios and one begins to feel a world away from the oscillators, filters, LFOs and ADSRs that subtractive synthesists are so comfortable with. Oh yes, FM synthesis is also thought to be the hardest synthesis method to learn, understand and put into practice.

Beginnings FM synthesis was discovered by Dr. John Chowning in the late 1960s whilst he was working at Stanford University in California. A short biography of Dr Chowning is available from the Stanford website where Dr Chowning is Professor Emeritus at The Center for Computer Research in Music and Acoustics. Link :

harmonics around the chosen pitch that can be controlled by the amplitude of the modulating waveform. It was Dr. Chowning's So, just maybe it is a subject that discovery of this harmonic effect, and could use a little demystifying. his hard work in figuring out how it Most of us will be familiar with using Starting this month and for a grand can be harnessed and controlled that total of six months we're going to take synths that have Low Frequency led to a totally new form of synthesis a look at FM synthesis from all angles. Oscillators. We can use an LFO to create a vibrato effect - the pitch of that has inspired musicians for nearly Over the course of this series we'll be the note being rapidly changed around four decades. We have entered into finding out about, and hearing from, the chosen note. Usually LFOs work at the realm of FM synthesis. FM's discoverer, Dr John Chowning. frequencies of less than 20 Hz - "rapid" We'll investigate the first popular FM Although we'll be looking at these is a relative term! Dr. Chowning took synths, journey into FM theory and things in more depth in coming the tremolo effect a (large) step then look at the current state of the further by using an audio rate articles this would be a good time to art in the soft synth plug-in world. introduce the basic vocabulary of FM Time permitting, we may even be able oscillator instead of a low frequency one. Using one audio rate oscillator to synthesis. Firstly we have to think to get a glimpse of the future of FM about Operators, a term which we'll affect (or modulate) another creates synthesis. 04

September 2011

Sept 2011  

Wsm Sept 2011

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