Entrance music

Entrance music (also known as an entry theme or walk-on music) is a musical piece or song that is played for athletes or entertainers when they first appear in front of the spectators before beginning a performance. Popular music acts may have recorded intro and/or outro music played before and after a concert performance, which is often of a different genre from that of the act's own live music. Acts often retain a single signature tune throughout their career; music acts typically retain the same intro/outro at least for a whole concert tour.
Professional snooker.
As part of Barry Hearn's vision for the future of the professional game, walk-on music was introduced from the 2010 World Snooker Championship. As of the 2012 World Snooker Championship, the last 32 players and their walk-on music was as follows:
Professional darts.
Walk-on music for professional darts players is typically either related to their nickname or their nationality. Some examples are:
Roller derby.
Walk-on music used in roller derby, also called "skate-out music", has been a part of the sport since its very beginning.
Major League Baseball.
The practice of using a heavy metal theme song to signal the entrance of a relief pitcher began at Qualcomm Stadium in 1998, when the San Diego Padres started playing "Hells Bells" by AC/DC to accompany Trevor Hoffman's taking the mound. "San Jose Mercury News" and "ESPN.com" wrote that the song should be honored by the National Baseball Hall of Fame and Museum. The use of rock and roll for entrance music emerged from the comedy film "Major League" (1989), in which relief pitcher Rick "Wild Thing" Vaughn entered the game to a cover of "Wild Thing" performed by X. In addition, batters will often select a song to play as they come to the plate in home games.
Wrestling.
Wrestling companies often have an inhouse composer composing theme music for wrestlers. They also may use stock music.
Many wrestlers have used many themes over the course of their careers. Some wrestlers like Ric Flair and Macho Man Randy Savage are known for their one particular entrance theme song, "Also Sprach Zarathustra" and "Pomp and Circumstance" respectively.