Use solid-state relays to blink the lights on your Christmas tree in time with music. Also good for Halloween haunted houses.
Get a nice large, healthy tree set up in front of your biggest windows. See How to Pick and Decorate a Christmas Tree for more details.
String lots of lights onto the tree. Use as many sets as you like, but arrange them such that there are three light regions, each with a separate plug. Run these three plugs down the trunk so they can easily be attached to the light controller. Up to three strings of lights can usually be linked in series, so you can almost certainly cover even big trees.
Plug light strings into the controller you built for Halloween: https://www.instructables.com/id/Solid-state-Halloween-controller-and-how-to-build-/ Attach computer and sound system. Select high-quality Christmas music and sync the lights with a winamp plugin: http://www.8-legs.org/ewilhelm/projects/2.165/index.html
Fire up the music, and treat your friends, family, and entire neighborhood to a great light now. If you really want to share, hook the music up to your outside speaker system and make the house shake in time to the music.