Open a Playground in Pharo.
Enter the following text.
(((ProcessorScheduler selectors)
�� select:�� [:each | each endsWith: 'Priority'])
�� collect: [:each | {Processor perform: each. each}])
�� sorted:�� [:x :y | x first <= y first]
Select it, the ctrl-i or "Inspect It" from a menu).
That gives you a list of the named priorities.
From that you will be able to answer your own question.
this is what I was able to put together thanks to your advice Richard.
https://www.youtube.com/watch?v=NFaR3ZQfOUU&feature=youtu.be
I am further developing this research on Pharo as a tool for live coding. I am sending many OSC messages and they sounds pretty on time if the Process is forked at Processor timingPriority.
is that the maximum priority?