Interesting article about the davoli synth on soundonsounds retro feature. Tells you what those grey keys actually do.
They actually turn on and off all the control buttons. Grey keys are for the whole octave select part, the black for the others. Interesting.
http://www.soundonsound.com/sos/nov06/a ... lisint.htm
"If you played the Davolisint with your right hand alone, you were not going to get very much from it. The sound ranged from a buzz to a rasp, with no filtering or shaping, and just vibrato to animate things. In fact, it was little different from playing a Vox Continental monophonically. The only things that gave it any sort of 'synth' quality were portamento and the ability to detune the two oscillators to produce a fatter sound, or to tune them at intervals such as a third or fifth. Or, of course, to detune them and apply portamento. Or detune them, apply portamento, and then add different speeds and depths of vibrato to each oscillator. Hmm... despite its limitations, it wasn't much like an organ at all, was it?
But let's now add your left hand into the equation. If you set up a basic sound using the control panel switches, you could use the bottom octave to articulate it in ways that would be impossible using a conventional VCO/VCF/VCA architecture. For example, let's imagine that you were playing with just the 16' octave selected, and no vibrato or portamento. If you then played, for example, a Cmaj7 chord in the bottom octave (the C, E, G and B keys) you added the 32', 8', 2' and 1/2' pitches to the sound, which changed its very essence by making it both deeper and brighter. This technique was great if you were playing accompaniment lines and wanted to make certain phrases stand out, or even stand proud as solo lines before dropping back into the mix again.
Alternatively, you could have no footages selected on the control panel, so silence reigned until you pressed a left-hand control key. Now, you could determine the octave of what you were playing by selecting the appropriate key with your left hand while soloing with your right. With a little practice, you could make the two-octave keyboard feel eight octaves wide by perfecting the technique of stepping up and down the grey keys as your needs dictated.
Now, what about the black keys in the controller octave? Using the C# and A# to add vibrato independently to VCO1 and VCO2 is not — as far as I can recall — a facility found on the performance panels of any other monosynth of the era. Likewise, being able to dial in three rates of portamento by playing D#, F# or both, is perhaps unique to the Davolisint.
So, all you needed was to perfect the technique of playing the white notes to add octaves to the sound, and the black notes to add animation. If you managed this, the Davolisint sprang to life, not as a replacement for a Minimoog or an ARP Odyssey, but as a viable alternative, an instrument in its own right. If you thought of it as an instrument in the same class as a Clavioline or Jennings Univox, you were on the right track, and that's no insult.
Oh yes, and the Davolisint had one final thing going for it: its price. At a little over £200, it cost a fraction of the price of a Minimoog or Odyssey, so it's not surprising that some players were willing to live with its limitations. What's perhaps surprising in retrospect is that so few were sold, rather than that so many were."