Our touch-guided oscillator/simulator is up on the iTunes App Store. Due to contract issues, it seems to have gone up the same day as the earlier Tune-O-Rama (9/3).

The specs for Leon’s original were simple: have one oscillator operate at a high but stable rate, and have a second oscillator vary over a predefined spectrum. Add the resulting waveform, and you have a sum that is an approximation of a sine wave created by the “beats” due to the frequency difference. Of course, the output is not a pure sine wave, and it’s all those little “dips” in the signal that give the original its unique tone. At the usual 44k resolution in digital audio, this is hard to recapture (theremin oscillators have frequency upwards 200k, usually), as the Nyquist Frequency for digital audio is in the order of 22k. Here, we tried to use a deterministic approach to render a waveform reminiscent to the actual instrument, where irregularities are provided in real time as determined by…previous irregularities.

There are a few snags: as screen resolution on the iPhone is 320 X 480, there is a linear ceiling of 480 discrete frequencies that can be mapped on the screen. Hence, for cases where finer tonal control is needed, Thereminator provides a frequency zoom feature to fit a smaller range on the screen at a time (by tapping, etc). There is also a glissando algorithm for providing a smooth transition from one frequency to the other, even in the case of hitting “blind spots” on the screen.

Although we can’t comment on the merits of attempting to fit an actual instrument on a phone (one remembers the words of the director of Blue Velvet), it makes a passable alternative to the real deal, especially in places where noise is a big issue. And it’s good for annoying friends as well (we did that a lot during development). Try flexing your finger up and down while touching the screen, and also side to side. The phone seems to pick up the heat and change the tone.