Simon, it doesn't work like that. The Virus does not have a notion of a 'unit voice', that everything else can be measured in terms of. You may be able to get 90 voices of plain saw waves with no modulation, but for anything musically interesting or useful, the polyphony is going to be less. The 'patch complexity indicator' on the LCD can give you a rough idea of how demanding your patch is, but it doesn't take into account unison or FX. The only useful measure is CPU load, but unfortunately, it is not displayed anywhere.
If you start with an Init patch (simplest = 1 bar on complexity indicator) and fill all Mod matrix slots, you'll see the complexity rise.
That said, it is well known that the biggest CPU-eaters in Virus are:
- advanced oscillator models (grain/formant)
- 'analog' filter mode
- reverb
hope this helps
