[DaveBlake]

Thanks for the links jasn, unfortunately no mention of rating there. I'm not being difficult, but I don't use iTunes or have example files so unless someone can tell me that there is tag data XXX that Kodi could process I really can't do anything.

Have a good look at the tags you have in your ALAC files using Mp3tag (ctrl+T shows all of them for a song in a popup dialog).

Can you tell me where it is stored in v16?

Read from the same music file tags song rating is stored in the rating field of the song table (having been converted from tag to a 0 to 5 value). In data migration to v17 this data gets doubled (to be out of 10) and moved to the userrating field, with rating field set to 0.