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Demo video: from vibrato to FM synthesis
I made a video to demonstrate the intimate connection between vibrato -- audible variation in a sound's pitch over time -- and FM synthesis:
http://jbj.raceriv.com/fm/Fm-Demo.wmv
[Edit: I have made a YouTube version for any Mac users unable to view WMV files.]
Very fast vibrato is the basis of FM synthesis. Here's what happens in the video:
1. You see on the left a carrier frequency playing at 128 Hz, and the modulator frequency (middle) is playing at 1 Hz, which means that it's going up and down once each second. This 1 Hz sine wave is controlling ("modulating") the pitch of the carrier frequency. The modulation intensity number (right) dictates how far up and down the pitch is going.
2. At around 0:20 in the video, I increase the modulation intensity, which makes the pitch go further up and further down on each cycle of the 1 Hz modulator wave.
3. At around 0:29, I increase the the modulator frequency. You hear a faster and faster "vibration" until it no longer seems like a "vibration" anymore, but a change in the tonal character of the sound.
4. At around 0:45, I bring up the modulation intensity. Rather than hearing the pitch go further up and further down as at 0:20, you hear the sound become brighter. The principle is the same: the change in the frequency of the carrier wave is getting larger. But the modulator wave is now moving so fast that you hear the frequency change as a "timbre change" rather than "pitch change."
This is the basic discovery that led to the development of FM synthesizers: that if you modulate (change) the frequency of a sound rapidly enough, we will hear it as a shift in the "character" of the sound, rather than as a "wobbling" of the pitch.
For those of you who have FM7 or FM8, here's a way of checking out this principle for yourself:
1. Open FM7/8, initialize a patch, and set it to play some note repeatedly.
2. Activate operator E and connect it to operator F in the Matrix.
3. Bring operator E's "level" setting all the way up to 100.
4. Bring operator E's "Ratio" setting down to 0.0100.
5. This means that operator E is playing at 1/100th the frequency of operator F, and you'll hear this as an "LFO-like" up and down movement of the synth's pitch.
6. If you activate operator D and connect it to operator E, you can decrease the ratio of D to near the same small level as E, you'll hear a more complex up and down motion of the pitch. This is because operator F is being modulated by operator E, but operator E is itself being modulated by operator D. In other words, operator D is influencing the speed at which operator E is changing operator's F frequency. Here's a little sound demo:
http://jbj.raceriv.com/fm/doublemodulation.mp3
Last edited by MrJiveBoJingles on Jul-16-2009 at 22:37
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