The wikipedia article[1] says it's "Fourier construction" but without reference (that I can find) and without elaboration. At their website[2] they list some of

The wikipedia article[1] says it's "Fourier construction" but without reference (that I can find) and without elaboration. At their website[2] they list some of their staff; I looked up research by one of their researchers and found a paper "Modeling and simulation of a grand piano"[3] which looks quite heavy on the physical modeling of strings and soundboard. I'd expect that to work better than spectral modeling because I think the latter would introduce (too much?) latency via needing to collect an entire spectral window (plus extra computation to compute the phases, and even then I don't think it could sound good enough?). Whereas physical modeling works directly in the time domain and there's a wealth of literature around it. See e.g. J. O. Smith III's waveguide synthesis work[4]. [1] https://en.wikipedia.org/wiki/Pianoteq https://en.wikipedia.org/wiki/Pianoteq [2] https://www.modartt.com/modartt https://www.modartt.com/modartt [3] https://hal.inria.fr/file/index/docid/768234/filename/RR-8181.pdf https://hal.inria.fr/file/index/docid/768234/filename/RR-818... [4] https://ccrma.stanford.edu/~jos/swgt/ https://ccrma.stanford.edu/~jos/swgt/