Sound file resynthesis. Although resynthesizing an analyzed sound file may seem pointless, many interesting variations can be produced by applying the Image Synth’s graphic tools to the image before resynthesizing. A simple starting point is to change the Image Synth’s resolution by altering the tuning, Frequency Map, or SPP setting. For example, try analyzing a short speech clip with the Micro8 scale. Then change the scale setting to Micro12 and render the clip at twice the SPP. Also try to set the tuning (using the tuning-fork icon on the top-right border) an octave higher.

Another effective approach is to change the input source used for rendering the picture. Again, analyze a speech clip. With the sound file still in the Sample Editor, render the image at four times the SPP using the Sample Granular input source. (The Sample Granular method is new in MetaSynth 2.7.) You’ll hear four somewhat different versions of the original clip because the grain must cycle through the sample four times to render the elongated picture. As an alternative, choose Narrow Noise from the Sounds menu before rendering the image with the Sample Granular input source. This produces a kind of outer-space radio effect, but the words remain intelligible. Finally, try applying some of the filters from MetaSynth’s Filter Palette to the noise sample before rendering.

Pitch and time effects. MetaSynth has three effects groups for quick picture modification (that is, modifications that you don’t have to paint in with the brush tools). The Hot Filters that are invoked using the buttons along the Image Synth’s lower-right border are time based; they modify horizontal aspects of the picture. The effects available on the Pitch and Harmonics submenu (on the left border with the notes icon) are pitch based and modify vertical aspects of the picture. Finally, the effects on the Process submenu (on the left border with the water-drop icon) modify the picture in both dimensions.

Because you’re working graphically, you’re not restricted to using any of these effects in their intended dimension. For example, applying a pitch effect to time is as simple as rotating the picture 90 degrees. Of course, there’s a tool for this, too. The button on the bottom border with the quarter-circle icon can be used to rotate pictures by dragging or by using numerical values. One effective application of this technique is to use the Add Harmonics pitch effect to generate an accelerating echo or “bouncing ball” effect.

This process works best with short, percussive hits with a little silence at the end. (If the sound file you’re analyzing has no silence at the end, increase the SPP setting by about 20 percent after fitting the Image Synth to the sound file.) The first step is to multiply the picture’s horizontal dimension (Size x) by four and set the vertical dimension to match. Next rotate the picture 90 degrees counter-clockwise by double-clicking on the rotate tool and entering “–90” for the rotation amount with “Wrap around” turned off.

Echoes are created by adding harmonics for each pixel in the picture. Harmonics are integer multiples (2:1, 3:1, and so forth) of the fundamental frequency. New pixels need to be inserted on the rows that represent those frequencies in the same columns as the original pixels. The Image Synth’s Add Harmonics process does this, and because it works relative to the chosen Frequency Map, you can spread out the harmonics by choosing one of the micro scales (Micro32 and Micro50 are good choices). Once you’ve chosen a scale, select Add Harmonics from the Pitch and Harmonics submenu. If you hold the Option key while doing this, you will get more harmonics, hence more echoes.

The last steps are to rotate the picture 90 degrees clockwise and restore the original Frequency Map. The harmonics now become echoes of the original pixels, and they die out because the Add Harmonics process adds harmonics with decreasing intensity. An interesting variation is to rotate the picture a little more or less than 90 degrees clockwise at the end—this will make the echoes rise or fall slightly in pitch.

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Reprinted with permission from Magazine, February, 2001
© 2001, Intertec Publishing, A Primedia Company All Rights Reserved