[Yvonnick Noel] I'm certainly no signal theory guru but I have worked for a while on a modal/additive synthesis engine (which the FTM roughly arrives at). While exploiting the parallel nature of the synthesis model is fairly straightforward, it still takes massive computational resources to produce musically useful results, calling for expansion beyond a single core, or even beyond the CPU. The subsampled polyphase filters mentioned in the second paper are a neat trick that provides sizeable efficiency gains, but this comes at the cost of signal quality and implementation simplicity; it also introduces model latency. I doubt that a free implementation of wide applicability will arrive soon. Tim