who composed its music?
Blake Neely
Flash vs. Arrow
Blake Neely 
when does the flash show up in arrow December 2, 2014 is this a film? It is an Arrowverse crossover event what do you mean by this first term you used in your answer? The Arrowverse is an American media franchise and a shared universe that is centered on various interconnected television series when was it launched? October 2012 can you name any two of such tv series? "The Flash", "Legends of Tomorrow", "Supergirl" does it also support audio series? Audio studio Serial Box is currently developing an audio series for it who developed the above crossover event we talked about? UNANSWERABLE where was it aired? On The CW
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Flash vs. Arrow [SEP] Music
On December 18, 2014, WaterTower Music released a selection of music from "The Flash"/"Arrow" crossover episodes, as well as two bonus tracks from their respective 2014 mid-season finales. Discussing the challenge of merging the themes of both shows into a cohesive score, composer Blake Neely noted that "It wasn't difficult because I originally designed the two shows to have styles and sounds that could merge and live together when necessary, but also hopefully stand alone as two distinct music worlds." The two bonus tracks were included on the album because "they proved very popular with the fans of the special event".