I've been working on getting some audio for Apollo 8 from the Honeysuckle creek audio. As of now, I have Launch through TLI and the 2 hours leading up to LOI done in 8-bit audio, and I'll post the work in progress shortly. Is there a way to have audio play in reference to something other then GET, like time from lunar periapsis?
Good!

There's not a lot of Apollo 8 audio on the website I know.
As far as the audio play reference is concerned, AFAIK, the only reference in orbitersound is with the timeline. Alain Capt managed to do something like you're asking for in AMSO and it's really amazing but it's a special code. Unfortunately We don't have such a feature in Project Apollo.