Don't get me wrong, NotePerformer has many excellent qualities and when it works right, it produces beautiful demos. But in certain contexts, its design causes a serious problem: loss of ensemble (synchrony) between solo instruments, especially solo strings in a chamber setting.
This is not a problem with the host notation software that NotePerformer is running under: Wallander Instruments says it is a side-effect of their building in random timing delays in their playback routines for strings, because individual players in a string section are always slightly out of sync with each other and that contributes to the realism of the sound. But unfortunately they do not special-case solo strings to make the timing more precise, even though that degree of asynchrony would be unacceptable in chamber music.
I've attached an mp3 of the beginning of something I'm working on, created by NotePerformer running under Sibelius. You can hear clearly that the viola is lagging the 2nd violin by at least 1/10 of a second in some places. This is horrible in my opinion.
I wonder if anyone else has encountered this problem and maybe found a hack to suppress it?