Agree with the two posts above. Phrasing and diction are crucial IMO to a good performance of any song, trad or otherwise, and it's an element of my own performance I've put a lot of work into over the last few years. Intelligent phrasing can go a long way even when you don't necessarily have perfect pitch; and we folkies can learn much from performers of other vocal styles (eg. jazz, classical etc.) in this regard.