The subtle variation of audio in reality is full of information for us. Audio for HCI should be as rich in information. This is difficult to achieve with a set of prerendered digital recordings. You could produce every variation before hand brute forcing a solution but the resulting number of .wav files would be unmanageable. A point which cannot go without saying is that any software-based solution for use in HCI must have latency characteristics that are below human perception.
Acceptable latency is a function of context.
If you start some music in response to a user input you might be able to accept a delay as large as 600 milliseconds. This is a serious issue for Microsoft operating systems. Finally, audio services must be at the system level like mouse support or keyboard input. Applications can get exclusive use of the one audio device. Instead, the system should virtualize the wave device.