Expert witness Todd Decker alleges “five or six points of similarity" between Perry's 2013 hit [Dark Horse] and the 2008 Christian rap song "Joyful Noise." Day two of the copyright infringement trial over Katy Perry’s 2013 single “Dark Horse” was characterized by more than one instance of live singing, but it wasn’t the pop star who was giving the performance. Instead, Todd Decker -- a musicologist and professor who serves as the chair of music at Washington University in St. Louis -- belted out some tunes during his testimony on Friday (July 19). Serving as the plaintiffs' expert witness, Decker...