In the Dave Manor (plant) side of Neighborville, there is a room that contains a set of large wooden piano keys on the floor. I think it covers one octave. This room can be found opposite the area where you can promote a character.
When you spawn on the plant side, facing away from the main manor (where you can find Rux), this area is to your left then up the stairs.
You need to walk/jump onto the correct keys in order to play the PvZ theme, which you hear throughout the game. As the achievement itself says, the theme notes are G# A G# A F D
Start on the second black key from the right (G#), walk diagonally down to the right onto the wooden key (A), back to the same black key (G#), back to that same wooden key (A), then jump down two wooden keys to the left (F) and then another 2 wooden keys to the left (D).EDIT:
If you're struggling with jumping, you can also walk off the piano keys after hitting the second A, then move down two keys and step back on to hit F, then repeat to hit D. Thanks to ManuxBakaTeam for highlighting this.
The noise made should sound like the PvZ theme (strange that), and a few seconds later, the achievement will pop.
Use the piano keys in the link below to help you:Labelled Piano Keys
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