This achievement can be obtained during the first 20 minutes of the game. Find Bomboman in Vellie. You can't miss his shop, in the central West part of the city. Pay attention to the rhythm he plays on his bongos (You don't even need to talk to him). Listen this rhythm several times. Then enter his house, just above him: you'll find some bigger bongos inside. You get it, you need to play the bongo song you just learned by jumping on them. Once you play it correctly, you will obtain a key that will open a hidden wall in Mesos later in the game. If you really can't figure it out by yourself, here is the correct rhythm: right, left, right, right, right, left, right.