SPECTRAL SYNTHESIS

How to use both your eyes and ears to design sounds

Spectral synthesis... the name evokes images of some ectoplasmic organist pounding out terrifying timbres in some gothic graveyard. Yet the term refers not to a spectre, but rather a spectrum – of the sonic variety.

If a spectroscopic spray of prismatic colour comes to mind, you’re near the mark. A spectroscope is a device used to split a light source into its constituent wavelengths. A spectrograph documents the results using photographic means. Such a document is called a spectrogram.

A specific type of spectrogram – called a sonogram – is a visual representation of a sound. You’ve seen them: brilliant displays of undulating colour or three-dimensional monochromatic displays that resemble some alien mountain range.

As a sonogram is a visual display, it’s only natural to consider manipulating the image in the same way a photograph might be, in Photoshop or GIMP. Aphex Twin fans will have seen the spectral spiral revealed in the sonographic representation at the end of Windowlicker, or the grinning mug lurking on its B-side.

The idea of altering or exploiting a visual representation of a sound can be inspiring, and there are a number of programs and plugins designed specifically for the task. Over the next few pages, we’re going to take a look at how you might use some of these programs to tweak and transform your sounds using the best dedicated spectral tools available. We’ll also show you how you might exploit the capabilities of other applications you might not have imagined would be suited to the job.

Along the way, we’ll examine the science behind the sound, explore a bit of additive resynthesis, and some of the image-transforming software used by experimental electronic musicians to plant those infamous subversive images into their mixes.

Need a break from conventional synthesis techniques? Then let’s fire up that graphics tablet (or mouse) and scratch out a new sound or two!