The music lens searches thru your music library. When the files containing the music are outside of the library, they are treated as files, not as songs. Is it really so strange?
How do you define "Music library"? Is it a set of all files imported to rhythmbox? But what if I use Banshee? Or, as I've been doing for the past few months, I use cvlc with files and folders typed on the commamd line? What would you consider my music library then? The whole concept of a music library seems passing strange in a world where files are everything.
Yes, it is really so strange. Or actually, it is really so brain-dead.
I am working on a search utility at this moment.
The first thing you want to do is figure what you're doing and adjust to your user's style rather than forcing them to adjust to your application's ideas. That is one key to a "it just works" application. Anything else is more-or-less stuck in the nineties.