I've often heard the advice that a bassist should learn to play things in every key. But when I listen to a bass line (or any piece of music for that matter), I hear it more as a series of intervals than as an explicit set of notes. They key of the song seems more a point of reference than a "box" in which I must stay. So if I want to transpose a bass line to another key, is there really more to it than just moving a little further up the fretboard?