Monday, May 09, 2016

Voltage Controlled Pitch à la Tomita?

I had this post drafted for a while but with the recent passing of Isao Tomita I finished it off.

Whilst researching the SS30 I noticed that it had been used by Tomita.

Isao Tomita - SS30 not pictured
Specifically our favourite strings machine was credited on his Daphnis et Cloe album (also called Bolero in the US)
As you might expect from someone creating synthesizer arrangements of orchestral pieces the albums credits also list a number of other synths which can perform strings duties, and another dedicated stringer, the Roland RS-202. It's hard to pick out the SS30 in amongst all that, but what struck me was that some of the string sounds seem to have pitch bend and even portamento applied.

The SS30 can't do that, but can I modify it to?

First I looked at the pitch control. Would it be possible to simply add voltage control to the existing pitch/detune control? The answer is yes, but the range of control would be very limited. The pitch and detune controls on the SS30 provide minimal control. You can tune it within a very narrow range but to get the kind of variation that's worthwhile it would need to be much wider. That would mean a completely new master oscillator design.
Also, the way that the square waves, produced the divide-down design, are converted to spiky saw-tooth-like waves depends on the frequency of each tone. If you shift the tone up or down you would not only change the pitch but also the wave shape and associated harmonics. So, pitch control isn't a good fit for this strings ensemble, or indeed any other of a similar design.

Rest in peace Isao.