Songfacts®:

• In the '70s and '80s, manufacturers of audio equipment often marketed their products as "High Fidelity" or its abbreviated version, "Hi-Fi," indicating that it could help create a quality listening experience. "Fidelity" also means loyalty, so if you have fidelity in a cause, you will not waver from it. In Costello's song, he uses the marketing jargon as a play on words, telling the story of couples who cheat (infidelity) and how they justify their actions.
• Costello wrote of this song in his 2015 book Unfaithful Music & Disappearing Ink, where he described it as "an incredibly sad delusion of a song in which a couple finds themselves in different rooms with different lovers, one of them still irrationally believing that their pledge will endure the faithlessness."
• "High Fidelity" is one of Costello's favorites. He explained in Rolling Stone: "This is a pretty exciting record. It's very raw singing and a great rhythm track. We cut it in Holland, where we had nothing else to do but go mad in the studio."
• A movie called High Fidelity was released in 2000. Starring John Cusack and Jack Black, the film (based on a 1995 book by Nick Hornby), is set in a record store where music geekdom abounds. This song doesn't appear in the film, but Costello's song "Shipbuilding" does. Among sanctimonious record store employees, Costello was a favorite, so it's fitting that he is on the soundtrack along with Bob Dylan, Stereolab and The Velvet Underground.
• In celebration of Elvis Costello's 70th birthday, Variety published a list titled "Elvis Costello Turns 70: His 70 Best Songs, Ranked." "High Fidelity" was #1. Variety said:
  
  "High Fidelity" comes close to being a pure distillation of what historically made so many Costello tracks great: It feels as urgent as a heart attack; it's haunting; it's filled with wordplay that somehow accentuate the deeply felt emotions rather being a distraction; it feels like something that is happening in your life right now, even if it happened 10 or 20 years ago; and it's over before you know it."