Do cello duets and have the Eb (baritone is nice w/ cello)player read bass clef like it was treble clef. When you read bass clef as treble clef and change the key signature it essentially transposes the Eb sax to C. For example a A in bass clef is a F in treble clef. But when you transpose that A(concert)to a Eb instrument it is F# (up a M6). That's why the key signature needs changed.