Not necessarily a bass question, but reading this thread - http://www.talkbass.com/forum/showthread.php?t=552814 - reminded me to ask something I've wondered about. Whenever I've read about modes and their corresponding chords (e.g. D Dorian corresponding to Dm7), the chord always includes the 7th. Never fully understood this, until one of the replies in the thread above mention that the 7th is a third above the 5th (obviously) - makes sense given that the rest of the chord is built in thirds too. Thing I don't understand - if you build a chord from the triad, you've got a complete chord that includes (pardon the amateurish terminology) whether or not the third is major/minor and the fifth is perfect/diminished (can't remember any modes containing an augmented fifth interval). Why add another third? Thanks in advance.