What is the name of the piano piece that plays during the marriage montage?

The piano piece that plays during the marriage montage is “Married Life.”

Composed by Michael Giacchino, the instrumental introduces the emotional story of Carl and Ellie Fredricksen in Up. The largely wordless sequence follows their relationship from childhood meeting and marriage through shared routines, hopes, hardship, and Ellie’s death.

“Married Life” was especially important because the filmmakers wanted the audience to understand Carl’s loss without lengthy dialogue. Giacchino first composed music for the sequence, then revised it after director Pete Docter asked for a sound resembling a song from a grandmother’s music box.

A common mix-up is calling the entire opening sequence “Married Life.” Technically, that name refers to the accompanying composition, while the broader prologue is often called the Up montage or opening sequence. The piece later became one of the film’s most recognizable musical themes and helped Giacchino win the Academy Award for Best Original Score.