Hi @Peter Fay, This is currently not an option but you may submit a feature request at https://ideas.ringcentral.com/.

A tad crude, but you can always record the ring tones to add to the front of your IVR greeting. (or insert them with your favorite audio software)

I was thinking about this for ours, as when you get the initial IVR audio - sometimes you get the whole start, other times it gets truncated. '...ve reached the Center, press...'