While playing Acorn, Netflix or Prime through Roku, the sound, especially music has a severe warbling effect.
I proved the problem was the Roku as I played the exact same moment of movie sound on Netflix via the Comcast app and the sound was perfect.
These things are just little special purpose computers. Like their big brothers sometimes you need to clear things out by restarting them.Restart via Settings > System > System restart (Or for Roku TV: Settings > System > Power > System restart)If a restart doesn't do it, try pulling the power plug to the device for a minute or so then plugging it back in.
Let us know how you make out.