Instructions
Watch as Embrose plays the drums. You don't need to pay attention to the notes he's playing -- just the rhythm, which you'll have to match when it's your turn. Wait for Embrose to stop playing and the camera to pan back to you.
Slide the stylus across the screen to select a note on the flute, and blow into the microphone to play that note. Each note is color-coded -- you want to play Purple, Yellow, Purple, Yellow, and finally Turquoise. Follow the rhythm Embrose set. When you've done this once, the camera will pan back to Embrose so he can play his half of the duet, and then back to you again.
Repeat the song when the camera returns to you. Once you've played it a second time, the task will be complete.
Try again if you don't play the song correctly at first. Again, it's one of the trickier ones, and Embrose's beat can be hard to match -- but with a little practice, you should be able to do it in no time.