What does Karaoke represent?

Karaoke represents Grandma finding her voice and overcoming her grief after Grandpa's passing. Grandma tells Iris a story shortly after they board the cruise ship about how her and Grandpa commanded an audience at a karaoke night on another cruise by teaching the audience enough sign language to sign along to songs with them. One night, Iris finds Grandma not in her bed, and then sees her doing the same thing herself elsewhere onboard. This moment is a turning point for Grandma as she is able to resume the activities she loves that she left behind after Grandpa's death.