Actually, now im coming back to hear what C-Eye has to say. I saw we take the discussion over to the DB side! 
For the record, playing an E over a D isn't going to sound good...at all. Dissonant yes, but a major 2 played over and over isn't far enough that it will sound like you know what you are doing, and it is close enough to make you sound like you just don't quite know where the note you are supposed to play actually is.
BTW, Ska songs don't usually have "keys". The bassist simply plays over the chords the guitar player is playing. That's not playing within a key.
For the record, playing an E over a D isn't going to sound good...at all. Dissonant yes, but a major 2 played over and over isn't far enough that it will sound like you know what you are doing, and it is close enough to make you sound like you just don't quite know where the note you are supposed to play actually is.
BTW, Ska songs don't usually have "keys". The bassist simply plays over the chords the guitar player is playing. That's not playing within a key.