Conversation so far:
what episode of supergirl is the flash crossover
Duet is the seventeenth episode of the third season of The CW television series The Flash and features a musical crossover with Supergirl.
who wrote the flash episode duet
The Flash episode Duet was written by Aaron Helbing and Todd Helbing from a story by Greg Berlanti and Andrew Kreisberg.

Question: can you tell me who directed the episode
Self-contained rewrite: can you tell me who directed the flash episode duet