[raichea]

File hashes are needed for every file in the library to uniquely identify them and this saves considerable time when using features such as the sync library feature. So it's most likely due to that (the hash is calculated during import now for new files). This has been in place for months though.

Mike

Thanks for that. 

It could easily have been happening for six months as I've not been playing much until a few weeks ago. One follow-on question though. The message pops up for songs that are in the same PDF, so is the hash calculated on a per song basis or just once per source file? It seems to be the former from my observations.