Drew hasn't been home for a while. He walks into his room and sees his guitar. He puts it away in the cupboard. Later, he explains that he used to play, but hasn't for quite a while. In the next scene, you see him take out the guitar from the cupboard and start to play. It is perfectly in tune! As a guitar player, no acoustic guitar would remain in tune for a month let alone a few years. He would have to retune each string one by one.
The background is terribly fake when the three of them are at the lake.