Favorites from the person’s late teens or 20s. Maybe because young adults are such avid listeners (and, back in the day, dancers), music from this phase of one’s life has been shown to be especially favored decades later.
Christmas music. You know yourself (whatever your faith!) how persistently some of these tunes pop back into your head once a year. It doesn’t have to be December for you to play old favorites.
Religious hymns. Someone who regularly attended services may welcome an album of classics.
Children’s music. Because very old memories tend to last longest, some older adults still connect with nursery rhymes. After all, they may have been heard both in youth and again when a young parent.
Jazz or bluegrass. Even someone who never was an aficionado may groove to a style with a strong bass line.