Re: Additive Synthesis

"Louise" <louise@xxxxxxxxxx> writes:

"Joe Pfeiffer" <pfeiffer@xxxxxxxxxxx> wrote;

"Louise" <louise@xxxxxxxxxx> writes:

Can anyone here explain or clarify what Additive Synthesis is?

As far as I know, it is the combination of sine waves to produce more
complex waveforms such as in the old Yamaha DX synths but surely that is
just called FM Synthesis?

No -- with FM synthesis, you take the original waveform and change its
frequency according to a second input. You don't just add the two
inputs together (as in additive synthesis).

So, FM synthesis is all about altering the frequency content by manipulating
the sine waves which act upon others to form the more complex waves. But,
if you used an FM synth and had all six operators producing only sine waves
at different harmonic frequencies, that could be called additive? Sort of
like an organ with different harmonics stops pulled?

No. It turns out wikipedia has a better description of how FM
synthesis works than I could hope to duplicate:
http://en.wikipedia.org/wiki/FM_synthesis. The deal is that you aren't so
much altering the frequency "content" as altering the actual
frequency. Because the frequency is being altered so quickly, the
effect is as if the waveform was being changed (and, before somebody
corrects me, in this case "as if" means the end result is the waveform
is actually changed).

Normally, when you added a few oscillators together you'd
do it to get a chord, rather than something recognizable as a
"different" waveform.

But if I was to add a piano, a trumpet, some strings and a guitar type sound
(or samples of these) together all on the same note at the same time,
perhaps filtered or effected in some way to create one whole 'sound' then
that would be additive synthesis?

You could probably argue that, but it would be really, really
stretching a point. Normally when you talk about creating a "sound",
you mean something other than the whole orchestra as a single sound!

Somebody else followed up by saying that additive synthesis works
exactly by adding individual sine waves together. I'd say that's a
pretty extreme view, but you generally want to think in terms of
adding at least simple sounds together, not something that's already a
real, sampled instrument.
.

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