Backstage

SPOILER

The clue for solving the puzzle begins at 6:17 in the video.

The following sequence is displayed in the fireworks:

5 stars
4 smilies
4 planets
4 hearts
5 butterflies
8 circles
4 cubes

Each shape has a musical note in the puzzle

cube, planet, butterfly - E
circle, smiley - D
star - C
heart - G
bug - F

Using the pattern from the fireworks to play the notes from the puzzle gives the song Begin the Beguine.

Answer is begin the beguine

(Note: There are differences of opinion on the shapes displayed; namely this solution doesn't mention the bug shape at all)