This song, a longtime concert staple for AC/DC, is essentially one long, double entendre-laden dirty joke. On the surface, the lyrics seem to chronicle the narrator's card game with a female card shark who ends up beating him with the card mentioned in the title. Of course, lyrics like "my ace was high" and "how was I to know she'd been dealt with before" give the song a different thematic shading that transforms it into a bawdy joke about catching a venereal disease. The minimalist melody that backs it up consists of simple blues chords, but AC/DC's recording of the song could be described as a blues shuffle on steroids: it rarely rises above a sleepy tempo, but Angus Young's thick riffing and the chant-like chorus give it intensity to spare. The crowning touch is provided by Bon Scott's vocal, which starts as a sleazy murmur but gradually build into a macho howl of anguish as he realizes "she's got the jack." Originally released on High Voltage, "The Jack" became a quick favorite in concerts because it provided a perfect opportunity for the audience to join in on its chorus (a good example of this can be heard on the live album If You Want Blood, You've Got It). In short, "The Jack" is a good example of the schoolboy-ish humor that infuses AC/DC's music.