“It’s very individualized,” Kim said. “It depends on the music, depends on what you like. But it also depends on if you believe it. If you believe that music is going to affect your performance, it will.”

During the series with the Mets, the batting-practice music designed to harass them added a quirky feel to the ballpark. Because the gates are typically opened around the same time that the visiting players take the field to get in their swings, the fans were greeted by slow, heartfelt ballads that sounded more appropriate for a karaoke bar.

“We like to be fun and creative with our in-game entertainment, and the songs we play during visiting team batting practice is part of the show,” Valerie Camillo, the Nationals’ chief revenue and marketing officer, said in a statement.

“Hopefully, our fans will find it funny, and maybe we can even get a smile out of some of the visiting team players,” she added.

This kind of strategy is not rare. Teams are always looking for an edge. The Yankees often play their own highlights during the visiting team’s batting practice. And in San Diego on Thursday, as the Padres prepared for their home opener against the champion San Francisco Giants, the home team took batting practice to a bouncy salsa tune. When it was the Giants’ turn, the music shifted to organ renditions of “Roll Out the Barrels” and “It’s a Small World.”

At Citi Field, the Mets play the same type of music for both teams. Maybe that has been their problem.

At least two Mets, Curtis Granderson and Daniel Murphy, said they had not heard the Nationals’ music over the last few days. David Wright said he was typically so focused that he tuned everything out. And the Mets, to their credit, won the series, two games to one. (It did not hurt that Matt Harvey cranked up the rock ’n’ roll in the Mets’ clubhouse on Thursday before he went out and shut down the Nationals for six innings.)