It has been awhile since Link has had a fully playable instrument in the Zelda series, but link must become a musician agian in The Legend of Zelda Spirit Tracks. Link must master a new instrument called Spirit Pipes which are Pan Pipes. Using the microphone you will blow into the DS to play this instrument while using the stylus to choose different colored pipes.
The pipes seem to be pretty standard for the Zelda series calling upon powers to help you through your quest. For example at one point you will need to play it in order to reveal the train tracks to get to the next temple.
The Legend of Zelda: Spirit Tracks is currently set for a December 7th in North America and December 11th in Europe.
(Source: Official Nintendo Magazine)