"A.M. Mayhem" is a documentary about Tucson, Arizona's first Hip-Hop station "Power 1490" KJYK. I haven't seen the film myself because the only public showing was last night at the Fox Theatre in Tucson although it is also available on DVD.
"Power 1490" played Hip-Hop and Rap from 1991 to 1995. They then switched to Modern Rock KKND "The End"--an abrupt format flip that remained a mystery but is apparently explained in the movie. Watch the trailer below: