MacOS – How to use an iTunes smart playlist to find and delete audio files

I just imported 300 AIFF files into iTunes in order to easily convert them to AAC. That part is done, and now I want to delete the AIFF files. I know how to do this from Terminal, but I'd like to find the best way to do this from iTunes.

I created a smart playlist with these rules:

• date added is 2/24/2012
• kind begins with "AIFF"

This smart playlist contains all 300 AIFF files that I want to delete, as expected. But when I select the files in this playlist, the Edit > Delete menu item is disabled, and the context menu does not display any menu items related to deleting or trashing the files. If I go to the smart playlist, select all the files, then change the source list selection to the entire Music library, the selection is lost.

Since my iTunes library only contains these 600 files, I could do the manual step of showing the Kind field in the list, sorting by kind, and selecting the 300 AIFF files. But I was hoping to be able to do this from the smart playlist. Does anyone know how to do this? Maybe I'm missing something obvious.

(Mac OS X 10.7.3, iTunes 10.5.3)