That doesn't make sense. You're confusing inside-emulation time with outside-emulation time. It's entirely possible to run an emulator for a frame at a time and get the sound right; the emulator just needs to run things in the right order or with the right internal synchrony.

It's also entirely possible to run an emulator at many times real-time and get the sound output correct, however you use it. You can use this to quickly get wav/mp3 copies of game music, for example.