If you are thinking about a musical Christmas light display it's not too early too start. Even starting in July may not be too early depending on the method you choose. If you will be writing code with delays based on a song then it could take a while to determine how long the delay should be for each note. I have started the code writing process, and am testing each song with LED's to check timing. I realize that it will change when I go to use relays because the take time to operate
Arduino Christmas Light Controller style
A collection of Christmas lights to music projects