That bug has been described on https://launchpad.net/distros/ubuntu/+source/rhythmbox/+bug/31821

"When creating a new "automatic playlist" in Rhythmbox when I specify to use the type "path" for the filter and enter "Hooverphonic" for example, this would mean all files in my library which have the word "Hooverphonic" in their paths would be selected.
The strange thing however is that Rhythmbox converts the entered word(s) to all smallcaps. Which results in all files with "Hooverphonic" in their path not being selected, since we are using a casesensitive filessystem.

Either leave the case as entered.
Or, this is what I would prefer, make the compare between the filter and the path of a file in the library case-insensitive so when entering "Hooverphonic" will result in selecting files with "Hooverphonic" as well as "hooverphonic" in their paths.
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> Thanks for your bug. What version of Ubuntu do you use? That works fine for me on dapper
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I am still using Ubuntu Breezy Badger (5.10), with the Rhythmbox package from the default install, which has version 0.9.0.

So the following example will work in Dapper?
file: "/home/loe/music/The Very Best Of Sting/01.flac"
will be selected when entering a filter on the path and entering "sting" (all lowercase).
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> Right the example gives the same behaviour with dapper
In case it was not clear the filter doesn't match the example"