There are a number of different approaches you can take to synchronize Christmas lights with music, though you will typically need to plan your display, use the proper equipment, and execute your plan. You should give yourself at least six months to properly plan and create your full display, though it can take longer, especially when doing this for the first time. This type of display can also be fairly expensive, so you should start shopping around and get an idea for how much you will need to spend on the lights, the hardware, and the software you will need to synchronize Christmas lights with music.
One of the first steps you should take is planning your display. This is likely going to be a fairly complicated process, so proper planning can save you aggravation in the long run. Before you do anything, talk to your neighbors and local law enforcement to address concerns about noise and light policies at night, as well as potential issues with traffic problems caused by your display. You should approach these concerns in a positive way, but be aware that you may need to address the fears of neighbors who learn you want to synchronize Christmas lights with music.
Once you have discussed your plans with your neighbors and authorities, you can begin working on your display. You should begin by deciding on how many channels you want to use; each channel is a separate circuit of lights that are all controlled together. Most beginning displays run about 32 channels, though you can use more. Once you know how many channels you want to tackle, you can then purchase the lights and decorations for your display.
You should look for the lights you want to use as early as possible. Shopping for Christmas decorations in January can be a great way to save money, as many stores drastically reduce the prices on lights and decorations to eliminate stock. You will also need to purchase a control system for your lights. There are premade systems that are quite effective, though they can be fairly expensive. If you have some knowledge in electronics, or you are willing to learn, you can also build your own system to synchronize Christmas lights with music, which is cheaper but can be much more complicated.
Once you have the hardware you need to synchronize Christmas lights with music, then you can choose the software to use. Prebuilt controllers typically have software provided with them; if you build your own controller, then you can choose free software to download and use with it. You will then use the software to choose your music and decide how your different channels of lights will change and synchronize with your music. The way this is done changes slightly depending on the software you use, though most programs will guide you through the process.
You should give yourself at least two months to program your display, though it may take longer your first time. Of course, you will also need to project the music for others to hear. Since your neighbors may not appreciate you playing music through speakers, you can purchase a small radio transmitter that will allow people to tune to your frequency and hear your music while watching your display.