Some information here, the beginning information might be useful:
Also, just to add, NotePerformer has its own support for SSO (2024) as an add-on to the purchase of NotePerformer. Many of us here use NotePerformer, either as the playback template itself or with the new Playback engines, using our sample libraries (only specified ones), so it takes all the expression map thing away.
NotePerformer
There is information on the Playback engines and demos of each library it supports near the bottom:
Just to make it clear, you purchase NotePerformer itself, then a separate purchase (should you wish) for the Playback engine to trigger your SSO library.
You will find various threads on NotePerformer here with a search.