Thanks to an MLB database, you can learn the title song and artist for every walk up song of each player on every team. So no matter what stadium you are visiting, you can instantly find out what song is playing. You can even listen to most of the songs with a quick link to Spotify.
A check in early June 2018 found the following songs being used for walk up music:
Javier Baez, Chicago Cubs: Chambea (Bad Bunny)
Charlie Blackmon, Colorado Rockies: Your Love (The Outfield)
Mookie Betts, Boston Red Sox: I Love My City (Ernest K.)
Manny Machado, Baltimore Orioles: Shut Up (Trick Daddy)
Max Scherzer, Washington Nationals: No Name (NF)