Allocation of row ids.

I'm not crystal clear on how row ids are allocated by DT.
Is it the case that, if my table initialisation includes an explicit definition (e.g. rowId: "song_id"), then whenever that table is in play the numeric part of rowId is guaranteed to be the song_id?
That's the way it looks, but I want to be sure. I'm asking because I need more aspects of my app to become generic, and using row ids is a significant step.