FIG. 1: You can create and modify pictures to render as sound files in the Image Synth (top). You can also analyze sound files to produce sonograms such as the three analyses of the word “welcome” shown at the bottom.

Analyze this. Analyzing sound files is a good way to get acquainted with the Image Synth. The process is as simple as loading a sound file into MetaSynth’s Sample Editor, switching to the Image Synth, and selecting “Analyze current sound . . . (n)” from the File submenu (shown as the disk icon at the top left of the Image Synth; see Fig. 1). MetaSynth performs an FFT (Fast Fourier Transform) analysis of the sound file and displays an editable sonogram. If you then render this image using sine waves, you will get a resynthesized approximation of the original sound file. The quality of the resynthesis depends on the resolution you have chosen for the horizontal (time) and vertical (frequency) dimensions of the Image Synth.

Fig. 1 shows the Image Synth Palette (top) together with an analysis of the spoken word “welcome” at three resolutions. The Image Synth’s frequency resolution is controlled by the scale selected from the Map menu at the top right of the window. From left to right, the three analyses were made using the Semitone, Micro8 (eight divisions per whole tone), and Micro16 scales. As seen in the pictures, higher resolution (that is, more frequency bands) results in a finer analysis of the sound file.

Getting around in the Image Synth. The Image Synth’s tools and pop-up submenus are arranged along the image area’s borders. Some of the tools are invoked by a single mouse click, and others by clicking and dragging in one or two dimensions. In the latter case, the Shift key constrains dragging to the horizontal, and the Shift+Option key combination constrains dragging to the vertical dimensions. Double-clicking on many of the drag tools provides access to additional parameters, and many Image Synth functions can be invoked by keyboard commands.

The Image Synth’s time resolution is controlled by the Tempo and Duration dialog, which is opened by double-clicking on the watch icon on the top border. Because the sound file’s length is measured in samples and the Image Synth’s width is measured in pixels, the natural unit of time resolution is samples per pixel (SPP). Fewer samples per pixel means higher time resolution but requires correspondingly wider pictures for the same size sound file. (Once you select the picture width using the Size x menu, MetaSynth can calculate the SPP setting required to fit the sound file into the Image Synth.) From left to right, the three analyses in Fig. 1 were made using 343, 171, and 85 SPP settings.

To better illustrate the differences in resolution, the pictures at the bottom of the figure show only the first few octaves of the analysis. There is, of course, a good deal of information above this, as you can see from the full view of the Image Synth (top of Fig. 1). In an analysis using microtonal scales, typically you will find large vertical clusters of pixels because the analysis smears over adjacent frequencies. During rendering, if the playback phase relationships are exactly right (or better said, exactly wrong), clipping can result. The solution is to lower the amplitude of the rendering input source. If this source is MetaSynth’s Wave Table Palette, simply use the Scale Tool (third button from the left) while holding down the Shift and Option keys.

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