The dancing lights were created from a photo of a Christmas tree taken with a moving camera. The handhold camera was set on rear curtain and slowly moved from left to right. The photo was treated with a distortion filter; some cloning had to be done afterward. The photo was copied; the flipped copy was pasted over the original, the upper half gradually decreased in opacity [transparency]. Both layers were merged and the exposure got adjusted.

Settings of original photo: f/6.3, exposure 1 sec, ISO 100, focal 5mm, no flash just the light from the tree