who composed the music?
Mark Snow.
Improbable (The X-Files)
The score for the episode, like the rest of the series, was composed by Mark Snow. 
what is improbable from the x-files? It is the thirteenth episode of the ninth season of the series "The X-Files". what is the plot? In this episode, Reyes and her fellow agents investigate a serial killer who uses numerology to choose his victims. Soon, Reyes and Scully meet an unusual man who may prove more of a hindrance than a help. who is part of the cast? Robert Patrick, Annabeth Gish and Gillian Anderson.
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Improbable (The X-Files) [SEP] Effects and music
Snow based much of the music in the episode on records made by Karl Zéro, on the request of Carter. Carter later noted that "I had heard his music and it was so far out and it fit with exactly what I wanted to do because I wanted to recreate [the yearly celebration in] Little Italy. [...] I wanted to create that festival."