fm synthesis is about this strange happening when vibrato is twisted
well past normal vibrato speed, it will start to
generate aliasing tones or phasing tones im not sure, but at the
beginning, if youve only got a sine wave oscillator with
a sine wave vibrato you cant do much with it yet, but you could have a
listen to what it sounds like, but thats just
to improve your chances after just using sine waves, you can use any
complex operator you wish, and you can even apply fm
to the fm and it actually works and will give you more sounds.
what ive tended to notice is you should position your fm frequency
still, and you should modulate your fm amplitude, amplitude
tends to sound better when its moving, and youll get a “moving” sound
when you put an envelope on your amplitude which will make
it sound *alot* better, because real sounds are always constantly
changing and youll gain that characteristic.
You can actually put an envelope on the frequency also, but its not
quite as thrilling as the amplitude.
an “fm” pluck sounds pretty good, and you do it with decaying the
amplitude of the fm oscillator and it sounds quite convincing.
so when i jump on an fm synth, im constantly testing frequencies,
enveloping the amplitude and modifying the operator waves until
i get the sound i like, which sometimes doesnt happen, im not quite
good at it yet.
But its quite fun, i got more than i expected out of fm, because i didnt
expect much i in fact thought it didnt work at first.
and thats about all i can tell you at this stage, but i cant wait for
Whats similar to fm is rm or am.
FM - take one sine wave and use its amplitude to modulate the frequency
of another sine wave
AM - take one sine wave and use its amplitude to modulate the amplitude
of another sine wave
RM - take one sine wave and add it to the second sine wave
They all sound pretty similar, but I like fm because its sound is more
obvious than am and rm, but am is still
nice it tends to make cleaner sounds if thats what your after, but you
use all 3 the same way.
Im a bit confused about am and rm, some people think rm is just am, and
rm is no different, but I think differently.
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I don’t think RM is adding two sine waves…I hadn’t heard the term
before (it apparently stands for Ring Modulation), but according to a
Google search it is multiplying two sine waves. This is just AM if you
allow the envelope to be negative, though usually in AM the envelope is
a much more slowly changing shape than the signal being modulated.
Yeh, im not quite sure on that… your probably right.
They are all modulations, which essentially adjust their respected
parts. FM only modulates frequency, not phase or amplitude. AM only
modulates amplitude, not frequency and phase, and so on. As an example,
an FM applied to a constant frequency would make it sound like its
pulsating (1950’s style alien saucer sound). An AM applied to a constant
amplitude would make it sound like it’s fading in and out. PM is a bit
of an odd one, but it generally sounds like static or like FM, but with
a higher pitch / noise.
Ring Modulation is just a DSP technique that applies a carrier signal to
the original source, and in this case it multiplies the two. There are
many DSP solutions that do this, but the most popular one is called a
Vocoder, which is an RM with an equalizer and band filter. It’s quite a
common practice when people want to simulate robotic voices.
RM = input(t) * carrier(t)
input = input signal (range: -1.0, 1.0, such as a song or voice)
carrier = carrier signal (range: -1.0, 1.0, typically a modulated sine
and t is some time value.
The real fun in DSP is when you get involved with Fourier Transforms.
Converting data into frequency domain, manipulating frequencies, and
then convert the signal back into time domain. It’s a little weird at
first, but amazing once you see the possibilities with it.
I forgot to mention, but check this site out. He offers a free PDF of
his book and it’s amazing. The best information you’ll get anywhere,
including how to use and interpret Fourier Transforms and perform DSP.