RIP
Frédéric L I am not sure Pianoteq is based on FFT…
QuasiUnaFantasia FFT does not seem at all relevant here,
Well, we can argue whether or not FFT is "essential" or "convenience" for PTQ and we can look at their patent(s) and paper(s) for that, but in any case it's just speculation, since the software is closed source. What is definitely true is that they do use FFT transforms (and inverse), as it is clear from https://www.modartt.com/user_manual?product=pianoteq&lang=en#intellectual-property
But you guys are nitpicking on a detail. My (admittedly poorly explained) point was "the CPU improvements these days are mostly coming from increased number of cores and only a few applications can take fully advantage of that", hence PTQ can not "ride" the CPU speed increase as many applications did before 2007. Yes, PTQ can "ride" marginal increases in overall CPU performance, which are still happening, but those are marginal. On the other hand, sample-based virtual pianos can "ride" the storage speed and capacity increases which are happening at faster pace compared to CPU performance increase. And I say that with discomfort, because from a software point of view I like PTQ much better, but the hardware situation is what it is. In the end, anyway, as @MacMacMac says
MacMacMac All that matters is the result.