The history of players choosing at-bat music is pretty hazy. The practice developed in a gradual, organic kind of way – and information on the subject is scarce – so it's tough to pin down when it started exactly. An article on an NBC affiliate websiteclaims that walk-up songs came into popularity after the '98 Padres started (on a whim, apparently) playing "Hell's Bells" to announce Trevor Hoffman's entrance into games. The fan reaction was so positive, the article claims, that other clubs quickly moved to copy them. Thus: at-bat music.