Playing around the middle range of the keyboard results in the prophet 52 to literally 'screech' as the two pulse oscillatros clash.
The attached memory should make it more obvious.
The issue is the Sync flag, the oscillators are not clashing but you are trying to sync one osc to another where the following osc is at a lower frequency. There are a couple of things here:
1. If you want to sync then the source should really be at a lower freq than the dest.
As they tend to the same frequency and especially where the following osc is at a lower frequency you will get a bad signal: one of the oscillators never completes a cycle before it is reset.
2. You will get better results if not syncing pulse.
3. I think the bristol code is actually wrong here and am searching for sources to confirm: I have OscA as the following oscillator, it should be OscB following.
If OscB follows then the FineTune gives some interesting harmonic changes. This does not really affect your problem: if the leading osc is higher than the frequency of the following osc you will get odd results.
So, OscA following OscB appears to be correct according to the owners manual.
I will have a look into the Prophet sync though. The bitone oscillators do this differently - an oscillator can generate a sync output signal as well as accept a sync input. In this implementation the sync output signal is a perfect square wave and when used to drive the sync input of another such bitone oscillator the sync is easier to derive. Perhaps I need to push this back into the prophet DCO too.