A complex sound rather similar to, but not exactly like, the "astrogator" sound effect heard in some bridge scenes of the original series of Star Trek.
Rather than merely modulating some pure tones, this approach uses a primary fundamental that is noisy, FM modulated, and amplitude-pulsed in a way intended to match the original sound, and then two separate filtering paths are used. The original sound appears to have been non-pure, probably a tape recording of some more organic sound, wavering, and send through a very peaky resonant filter to create the upper-frequency chirps. In my case, I built an analog box circuit to all the upper frequencies portion to come mostly from the third harmonic of the fundamental as it excites a resonant filter. But it isn't exact. Getting something to sound just like the original seems nearly impossible, other than by direct sampling of course. But with the analog box circuit, I can vary all sorts of parameters. So this particular sound clip is built from 3 different circuits, two of which used the dual-filtering paths from a noisy oscillator as described above, and another that used a more spectrum-based analysis alone. These were combined into one circuit and I saved some output while varying certain parameters. I then edited the result in Cool Edit Pro to overlay two separate segments with chorus on one and flange on another, and worked the ends to form a loop. No, it doesn't sound just like the original, but it is a fun and similar-enough sound that it might prove useful to someone for something.
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