I can say that to me, one of the most powerful things in the world is music. I have used it to learn how to cry , to feel and to smile. For some reason , sometimes the only way I can find my emotions is to listen to a certain song, maybe it was my mother's favorite and it just makes me feel closer to her.
Listen to your friend's songs, and you will feel connected to him by them. It is like hearing a message from someone who has left us, because if it was really a special song to them, that meant that song is how they felt, and maybe we didnt know it while they were alive how deeply they felt about something. It kind of keeps them alive in that way.