So, how about this 'spectral synthesis'?

[cosmosis]

Hello all!

Lately I've seen some talk about spectral this, image that. I saw a few vids where they imported and edited images into Alchemy or created some from scratch, and selected/cropped parts of the spectra in Iris, and it all seem pretty interesting. Besides those things I saw, I really don't know anything else about this spectral thing, and synths in general, some classic subtractive patching, so please be gentle

Are there any other big things about this 'spectral synthesis'? Is the spectral aspect limited to editing in the frequency domain (or an image?). If so, are the sounds produced accross the keyboard merely stretching or is there some kind of unique form of synthesis after the editing is done?

And are there any interesting free tools that I can experiment with and maybe learn some (Alchemy/Iris/Harmor and such are out of the question ATM, but feel free to talk about anything!)?

BTW, I have done much editing in spectral view in audio editors, so I do understand the spectral view at least

PEACE!

[Gone soft]

I'm not 100 % sure about the precise definition of spectral synthesis, so I'll leave that to someone else to explain. For some recommended free software see this thread, ignore the two or three or so payware suggestions. Page two only has a post that says + 1 for Spear or something like that so only the first page is really relevant.

[ZenPunkHippy]

Spectral synthesis is based on FFT (Fast Fourier Transformation):

http://en.wikipedia.org/wiki/Fast_Fourier_transform

A little more info here:

http://en.wikipedia.org/wiki/Spectral_m ... _synthesis

The audio is split in to what are known as spectral bins. Each "bin" represents a specific band of frequencies e.g. 20 Hz apart. Because the audio is split in to bands, each of these bands can be manipulated in isolation which is not possible using standard VA synthesis or subtractive techniques.

For example, you could boost the amplitude of frequencies in a specific range, without affecting any other parts of the sound. Compare with subtractive VA synthesis, where the filter or EQ will always boost "around" the chosen frequency.

FFT is also used for additive synthesis, which is different again. One of the benefits of using spectral techniques is very clean re-synthesis, which is better suited to some types of sound, especially with complex sounds e.g. a drum loop where there are lots of different elements. Additive works better with pure tones.

The Alchemy manual also has some useful info:

http://www.camelaudio.com/alchemymanual ... al-editor/

Peace.
Andy.