The musical instrument is perhaps one of the key parts of the Zelda series. The timeline hardly makes sense, the lead character is a bit anti-social and Zelda is becoming increasingly odd looking, knowing that there is a magical instrument with which to banish evil is very comforting.
This time around it's the harp that's the focus of everything, and boy does it have some powers. You'll play the instrument by moving the MotionPlus in time with a pulsing circle (as seen at 1:26 in the video above). Not the same as memorising all those great Ocarina of Time songs, but I'm sure Skyward Sword will make up for it in other ways.
I think the best thing about this trailer is the portion in which Link actually acquires the harp (which a little research tells me is actually a lyre). Interestingly enough, the harp from Skyward Sword is the same one used by Sheik. What bearing will that have on the plot?
Only a few weeks until all is revealed.