Kodamo EssenceFM, User Manual

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First steps
Introducing FM synthesis
FM stands for “Frequency Modulation”. A waveform is multiplied (“modulated”) with
another one to create a new sound. It’s the same as vibrato, except that it is much faster,
so much that it sounds like a different timbre to the ear, rather than a quick vibrato.
If you’re familiar with the subtractive synthesis used in analog synths, FM is quite the
opposite: you usually start from sounds with low
harmonic content (e.g. a Sine Wave), that once
modulated will create more harmonics.
The new harmonics, sometimes called “Partials”, depends
on the frequency ratio between the carrier (the base
sound) and the modulator (the one modulating the
carrier’s signal).
In FM synthesis, a block generating sound is usually called an Operator, and the Operator
arrangement is called an Algorithm.
An FM Algorithm is usually represented as below, and is to be read from top to bottom.
When an operator is feeding its signal into another one under it (1, 5 and 6) it is called a
Modulator -you don’t hear its direct sound-, while operators at the bottommost (2, 3 and
4) are Carriers .
Changing the volume of a carrier will effectively change your sound’s volume, but doing
the same thing on a modulator with modify the harmonic content of the sound. This is
where the power of FM synthesis resides! Coupled with envelope generators, harmonic
content that changes over time is easily achieved.
There may be several modulators for one carrier, in this case their output is simply
summed before the modulation happens (additive synthesis). Or there may be a
modulator modulating several carriers, in that case its output is simply sent to each
carrier.
The operator 1 has a small number on its top right corner indicating its feedback source.
A feedback is simply another link between two operators, except that it can feed into
itself (which is the case on the picture above). This is used to alter the tone of the
operator, providing more and more overtones as the feedback level is increased. It can
be used as a noise source when pushed to the max.
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