Hi Joe,
I think that the issue here is that although the Brennan uses the physical file names and track names to manage the music collection, the Sonos uses the tag data (the metadata) that is stored inside eack trackname.
You can access this metadata and modify it if you download an application like 'Mp3Tag' (which is a free download). This is an excellent product, especially if you have a largish collection to update.
Regards,
Peter.