The song "Someone Else's Heart" by Elvis Costello is about two individuals who discover that they have both been nosy and read each other's personal letters and diaries. The lyrics describe how they both realize that love is not new or exclusive to them, as they find similarities in the emotions and experiences expressed in each other's writings. The protagonist acknowledges that the words they read remind them of someone else's heart that has left a mark. They feel a connection to this unknown person, perhaps realizing that heartbreak and longing are universal feelings. The mention of pop music playing on the radio and people on the streets whom they do not know further emphasizes their feelings of detachment and isolation. As they delve deeper into each other's pasts, they find that despite the initial invasion of privacy, their love for each other is genuine and strong. They indulge in exploring each other's previous relationships, understanding that these experiences have shaped who they are. The chorus emphasizes that though the words and hearts may be different, the underlying emotions remain the same. The past relationships of both individuals are acknowledged (so much for him, so much for her), but they accept that those relationships are now in the past. They have found solace in the fact that they both know about "that someone else's heart." Ultimately, the song portrays a connection forged through vulnerability and understanding. The protagonist and their partner have discovered that love is not exclusive to them, but their love remains true enough to withstand the challenges of exploring each other's pasts.
