Sonic Analysis - has processed 6 albums in 40 minutes

If you’ve already updated to PMS 1.24.3 you can do this:
Create a new advanced server preference, named LongRunningJobThreads
It can contain the number of threads which PMS shall use concurrently for sonic analysis.
Careful not to exceed the number of your physical CPU cores (hyper-threading doesn’t count).
A sane strategy would be to leave 1 core as spare.