I loaded c. 50 albums, resaved them, then went to delete them.

The removal of the albums takes several minutes, during which time the UI is locked up. 

I suspect that the cause is metadata summarisation. When I select all albums, it tries to summarise the metadata across the 794 tracks, which takes some processing time, and then as it removes the albums one by one it tries to resummarise the metadata.

We really need to look at:

1. When metadata is summarised - we should definitely have a short delay of (say) 0.5s before we start to summarise, in order to allow further UI changes (e.g. selection of another album) to happen.
2. We should ensure that the summarisation does not lock the UI and is interruptable if you change the selection.
3. We should try to look at a better algorithm whereby we precalculate the summary for an album, and then summarise across all select items by summarising all selected albums and then adding any individual tracks that are also selected.