Spectacular synesthesia video. The official music video for Ljósið by Ólafur Arnalds.
syn-es-the-sia n. Physiol. Sensation produced at a point other than or remote from the point of stimulation, as of a color from hearing a certain sound (fr. Gk, syn = together + aisthesis = to perceive).
Not exactly sure how this was made, but it seems pretty obvious that it is a computer generated effect. Probably using [Sound → Color Synesthesia] mixed with particle effects and fluids/smoke. I would not be surprised if this was a plug-in for After Effects or something similar.