- n. A fastball thrown near the batter's chin, often to set up a subsequent pitch thrown low and outside.
'Chis music' originated in the late 1800s but with a different meaning: idle talk or chatter, or heckling from the fans. It came to be a synonym for a brushback, 'an inside, usually high fastball intended to force the batter to move away from the plate,' in the 1940s.
“You may remember Noles as the fellow who, as a Phillies reliever, knocked down George Brett on an 0 and 2 count in the fourth game of the 1980 World Series with what is blithely called ‘chin music.’”
“Call it chin music, a little baseball serenade designed to keep batters loose. Pitchers believe the inside part of the plate belongs to them. Crowd it and the response is a brushback or, as Satchel Paige termed it, 'the ol' bow-tie pitch' - a message from hurler to hitter not to get too comfortable up there.”
“It is 'so accepted by custom that a pitch intentionally thrown at a batter has its own terminology: 'brushback,' 'beanball, 'chin music.”