I found that our machines are all generally really fast compared to the 1mhz ]['s. Because of this, it makes more sense to let the emulator overclock when the disk drive is active than it does to hack the emulator for some convenient speedups. Compatibility is the chief driver, but also it's easier to save the emulator state if everything runs as originally intended.
I set JACE to overclock when the Disk ][ controller is made active, and then the overclock is disabled when sound is active. Hence, you can leave it running at max speed and it will still produce the same tonality of sound because it slows down until the speaker goes dormant again.