Lucy the cat came this summer again to visit her friends in Hellas, Calenina the cat and the patient tortoise.
Just after porridge breakfast they were listening to FM radio and suddenly Lucy started showing off again.
"Listen, it is the 80's song Maria Magdalena - Sandra. The fabulous bass comes from the Yamaha DX7 synthesizer. All these sinewave operators. Some of them frequency modulating other ones...."
The patient tortoise started getting angry, Canelina could not understand a thing and started crying. She decided to head down at once on the beach to find the wise seagulls so that they can explain to her how FM synthesis works.
It so happened by chance that the 2 wise seaguls had with them their small portable Yamaha PSS-480 synth. It is an FM programable synthesizer with just 2 operators making much easier understanding the foundation of FM synthesis. Furthermore it is 9V battery operated, has 2 small speakers and the wise seagulls just used a somewhat small 9V solar panel to power it.
Canelina the cat could not stop crying and the wise seagulls immediatly started giving her examples, first without even using any keyboard.
"Operators are just pure sinewave generators. They sound like a tuning fork. Would you sing for us the purest and steadiest tone you can?"
Canelina certainly could do and started niaouing a near pure steady tone with as less overtones as possible.
"Great, could you now add some vibrato?"
Certainly she could. She started singing her tone and slowly reducing then increasing and back and forth her pitch around the pitch of the tone she was singing.
See, that's easy. This is called frequency modulation as you change the frequency of your vocal chords vibration around a mean frequency which is called carrier frequency which is really the frequency you sing.
Canelina started wiping her tears.
Can you now start increasing the depth of modulation or depth or degree of your vibrato.
Certainly she could. And she started changing frequency smoothly and broadly up and down like an ambulance.
Can you now go back to a small modulation index but increase the rate, ie the frequency of your vibrato?
Certainly she could. But it was not easy. Her tone was already going little up and down in frequency fairly quickly.
Can you do it faster. Faster...
She could not, so the wise seagulls started playing with her shaking her very quickly, gently tapping her belly or back at a very high frequency (fast rate) until she produced such a funny tone that they all burst to laughs...
See... that's it. FM or frequency modulation can produce very rich frequency spectra. Usually one operator is connected to another. This means one sinewave modulates the frequency of another sinewave. One is the cat and the other is the seagull shaking the cat back and forth while she tries to sing. By changing the parameters of frequency and how the amplitude of each operator or oscillator varies, various timbres varying in time can be created.
Canelina jumped from joy. She called all her friends to the beach and they all started dancing and singing Maria Magdalena - Sandra under the sun rays of light that do not leave any shadow to the truth.
See also:
DX7 operating manual
FM Theory and Applicatiins from musicians to musicians - Chowning, Bristow
John Chowning (discoverer of FM synthesis) or (David Bristow co programmer of DX7 voice presets) interviews on YouTube.
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