Forty is the birthday where people start looking back without feeling old yet. There is enough life behind them to have a soundtrack, and they still remember where they were for most of it. That is what makes it a good year to give someone their own songs back.

For anyone born in 1986, those songs fall into four clear chapters: the year they arrived, the childhood they half remember, the teenage years they remember completely, and the adult life that came after. The best 40th birthday songs are not the forty biggest hits. They are a few from each chapter, chosen for the person.

The year they were born: songs from 1986

They did not hear these the first time around, but they grew up with them on the radio in the kitchen and in the back of the car. Opening a 40th birthday playlist with a song from 1986 is a small way of saying this starts at the beginning.

"Livin' on a Prayer" by Bon Jovi is the obvious one, and obvious is fine at a party. "Papa Don't Preach" by Madonna, "Kiss" by Prince and "Walk Like an Egyptian" by The Bangles all came out that year and still fill a room. For something gentler, there is "Don't Dream It's Over" by Crowded House or "True Colors" by Cyndi Lauper. For the one who always preferred the quieter corner of the record store, "There Is a Light That Never Goes Out" by The Smiths.

Childhood: the nineties in the background

Between five and eleven, music is something other people choose. It still gets in. "Smells Like Teen Spirit" by Nirvana, coming from an older sibling's room. Whitney Houston's "I Will Always Love You", everywhere for months. "Wonderwall" by Oasis and "Waterfalls" by TLC on every station. And then the first songs that felt like theirs: "Wannabe" by the Spice Girls, "MMMBop" by Hanson, "Torn" by Natalie Imbruglia.

One or two of these is enough. They are the songs that make a forty-year-old say they had forgotten that one, and then sing every word.

The teenage years: 1999 to 2004

This is the chapter that matters most. The songs people hear between thirteen and eighteen tend to stay with them for life, and someone born in 1986 was a teenager at an unusually good moment for pop.

"...Baby One More Time" by Britney Spears and "I Want It That Way" by the Backstreet Boys opened it. "No Scrubs" by TLC and "Say My Name" by Destiny's Child were on every school bus. Then came "Yellow" by Coldplay, "Ms. Jackson" by OutKast, "The Middle" by Jimmy Eat World and "Last Nite" by The Strokes, depending on which table they sat at. "Complicated" by Avril Lavigne, "Lose Yourself" by Eminem, "Crazy in Love" by Beyoncé and "Hey Ya!" by OutKast carried them to the end of school. "Mr. Brightside" by The Killers arrived right as they turned eighteen, and has not left since.

If you only have room for a handful of songs, take most of them from here.

Their twenties and after

By now the songs are tied to real events: a first apartment, a wedding, a long drive, a child. "Hips Don't Lie" by Shakira and "Rehab" by Amy Winehouse come from the year they turned twenty. "Umbrella" by Rihanna, "Viva la Vida" by Coldplay and "Use Somebody" by Kings of Leon belong to the summers that followed. Then "Rolling in the Deep" by Adele and "Dancing On My Own" by Robyn, and later "Get Lucky" by Daft Punk and "Uptown Funk" by Mark Ronson and Bruno Mars, which were probably played at every wedding they went to.

For the most recent years, choose by memory, not by chart. One recent song that belongs to something you did together says more than three that were merely popular.

How to turn the list into a gift

A playlist of sixty songs is a background. A mixtape of eighteen is a message. A CD holds about eighty minutes, which is close to twenty songs, and that limit is useful: it forces you to pick the ones that are really about them.

Take two or three from 1986, two from childhood, seven or eight from the teenage years and the rest from adult life. Then put them in the order they were lived, so the disc plays like a short biography. There is more on how to pick the right song order for a mixtape gift if you want the sequence to carry some weight, and a full guide on how to make a birthday mixtape someone will keep forever.

If the birthday is for someone ten years older, the same idea works with a different decade, and there is a matching list of the best songs for a 50th birthday.

Forty years is long enough to fill a tape and short enough that every song on it still means something. When you're ready, start creating your own mixtape.