The easiest place to get this achievement is in the 4th level, St. Crux Cemetery. From the start, keep going right, killing the zombies along the way. In the 4th section you will reach a pit that you need to jump over. In the next area you'll have to kill a few more zombies until you get to the guitar. Press

to start playing and at some point in the song just press the guide button on your controller. It's the button in the middle that looks like

.