Try to do that with a factor of e.g. 10 (you would likely need a factor of 1000 to cope with a "composition" of millions of notes) and observe the quality. The "physical limits" (e.g. Nyquist rate) also apply to the calculations done by a computer. To cope with the speed-up of slow motion to real-time you'd have to re-sample or transpose. Even with a very large sampling rate both of these transformations only produce useful results within narrow limits (less than an octave, i.e. factor two).