Nice post Timo!
I'm not so sure that the doubling of the second filter does, in fact, happen under-the-hood though. Always thought that's a consequence of how the Virus handles the merging of the two signals. I also suspected this to happen, but then thought it ought to charge the DSP the same way a "twin" unison would, it would have to make a double, right? And just didn't notice that load, after some tests.
But I'm not 100% positive about this, of course. Keep'm coming!
