When Mariah Carey released “All I Want for Christmas Is You” in November 1994, she gave the world much more than a seasonal hit. A vocal tour de force, an immaculate composition and a fan favorite, it has become the top-selling digital holiday song of all time (according to Nielsen Music), the inspiration for countless covers and -- having just re-entered the Billboard Hot 100 for the seventh time (where it looks poised to finally reach the top 10) -- a pop hit for the ages.

The Ultimate Tune For That One-Of-A-Kind Voice

Pop and Broadway vocal coach Liz Caplan (Ben Platt, Neil Patrick Harris) on the technique behind Carey’s sonic acrobatics.

This song was written with one person in mind, and that person’s body, voice and heartbeat. Especially at that time in her mid-20s, Mariah Carey’s vocal registers -- her chest voice, her mixed voice and her upper whistle-tone sounds -- were so in balance, so symmetrical. With almost every note she sang, you heard all the frequencies of her instrument. She’s so clever in how she uses all the elements of her voice: She starts off in a very wistful mixed tone, then digs into the lower parts of her voice, then gradually starts riffing and goes into her mixed and whistle tones, and it’s one unique streamlined voice.

Singing itself is internally aerobic, and there’s not a lot of space between phrases in this song. You want to make sure that the breath you take is so well-anchored that you have tons of steam to let loose during the course of a phrase. Even when Carey uses breathy tones, it’s purposeful usage of breath to get that sensuality through -- an attachment to a deeper meaning. The “you” is the part where the voice has to portray yearning without speaking.

Two sections are the biggest challenges. The mini climax at the end of the bridge (“Santa, won’t you please bring my baby to me”) is all repeated notes. It almost feels like she’s stamping her feet defiantly, but it feels grounded. It’s difficult for a singer to make those notes even and prominent but not draw attention to the fact that they’re repeated. And toward the end, when she’s popping her voice up, “You, baby,” her voice goes up and up, but she’s not honking it out.

The background vocalists are actually doing a lot of the heavy lifting. They’re like the support beams for the bridge. The song is like a runaway train, and even if you have sung it your whole life, you might realize you’re not quite prepared to connect register to register. I’d do an entire vocal warmup just for this song.

The Gift That Keeps On Giving

Three of the genre-spanning artists who’ve tackled Carey’s hit on their cover strategies.

Lady Antebellum (2010)

“It sounds like a happy song, but it’s actually a longing song,” says the country trio’s co-lead vocalist Charles Kelley. “Country is known for its heartbreak, so that’s what we tried to bring to it.” The approach: Slow it down (the original is “kind of in double-time,” he says). Lady A’s cover, released on its EP A Merry Little Christmas, peaked at No. 38 on Hot Country Songs in 2011.

Hanson (2017)

The band of brothers didn't want to mess with the tune’s DNA when it recorded the song for new album Finally It’s Christmas. “For a band that harmonizes, it makes a lot of sense,” says Taylor Hanson. “The distinct difference in our version is the sound of a band playing, digging in a bit more on the bridge with heavier guitars, having a more organic sound with horn parts and the piano leading.”

Charly Bliss (2017)

“We are fully out of the closet in our Mariah fandom,” says the indie-pop quartet’s singer, Eva Hendricks. Its cover “was about finding balance between keeping the upbeat nature and scaling it back, making it sound like one of our songs.” To reach for Carey’s vocal heights, “I never sang full-out until we recorded it,” says Hendricks. “I was just like, ‘I think I can hit these notes.’”

OTHER COVERS OF NOTE My Chemical Romance (2004) • Jessica Mauboy (2010) • Newsboys (2010) • Big Time Rush (2010) • Glee’s Amber Riley (2011) • Michael Bublé (2011) • Cee Lo Green (2012) • Fifth Harmony (2014) • Idina Menzel (2014) • She & Him (2016) • Lindsey Stirling (2017)

-- TAYLOR WEATHERBY

Mariah’s Songwriting Science

Composer-artist Owen Pallett explains why this modern carol sounds so classic.

THE HOLY MELODY

“The song’s melody is straight as anything -- one syllable to a beat, quarter-notes all strung along in a row. This is how hymns are written. Compare ‘Angels We Have Heard On High,’ ‘Hark, the Herald Angels Sing,’ ‘Oh Come All Ye Faithful’ or ‘Good King Wenceslas’ -- all of them are hymns; all of them possess that particularly Episcopalian grace.”

THE MAGIC CHORD COMBINATION

“Mariah’s chords are borrowed from the mid-20th century canon of Christmas favorites -- the stuff Bing Crosby made famous. She uses ‘flattened six’ chords, which happen when you take the sixth note of your scale -- an A, if you’re in the key of C -- and lower it to an A flat. The flattened-six is pure, uncut coziness, as heard in ‘White Christmas’ and ‘I’ll Be Home for Christmas.’ You can hear the same salted-caramel lusciousness when she sings, 'Something I can call my own/Don’t need you to come back home.'"

THE WARM, FUZZY FEELING

“At the end of all of her cadences, Mariah switches to a five-flat-nine chord: ‘All I want for Christmas is you.’ The particular color of that chord should trigger well-worn synapses associated with ginger cookies and grandmas. ‘I’ll Be Home for Christmas,’ ‘Silver Bells,’ ‘Chestnuts Roasting on an Open Fire’ all wield that particular emotional dagger of sentimentality. And what is a five-flat-nine? It’s just a V chord with a little extra note thrown in -- the aforementioned flattened-sixth.”

THE FAMILIAR ECHO

“Notably, Mariah’s opening salvo on her vocal melody is only a note or two removed from ‘I Saw Mommy Kissing Santa Claus’ and the intro to ‘Mr. Sandman.’ It’s definitely not plagiarism, but it’s enough to trick you into thinking this melody is an old friend. And it’s one more reason this classic song will forever guide us toward overspending on lavish gifts.”

She’s Got Me Feeling Emotions

Poet, author and Mariah superfan Hanif Abdurraqib on growing up with “All I Want for Christmas Is You”

I didn't grow up celebrating Christmas, but I did grow up celebrating Mariah. Music Box was the first album I purchased with my own money; by the time “All I Want for Christmas Is You” came out, one year later, I was prepared for Mariah to be the sole reason for my Christmas to mean something. I would listen to it on headphones at the start of winter break as a kid, dutifully but regretfully retiring it every Dec. 26. It was the one holiday indulgence I allowed myself.

All of the best Christmas songs are also love songs, and “All I Want for Christmas Is You” is the one that’s most honest about the fact that what we really want during the holidays is a warm body to share a bed or a couch with. In the music video, that someone is notably missing. We see Mariah kick around alone in the snow, revel in opening gifts alone, twirl around a tree solo, sometimes petting a dog. And it feels right: Somehow that tone of bittersweet absence is what makes the song work.

Now, when it is cold enough to heat up a mug of anything warm and sit on a couch in winter, I find that I still want the kind of companionship that Mariah sings about. Most of all, I want the feeling that listening to “All I Want for Christmas Is You” has always given me. In every box I open on Christmas morning, I want what I feel when the percussion first kicks in. I want to open a box with not only Mariah’s signature high note at the end but also the anticipation of that note -- the gift that we wait for eagerly, hoping for its arrival, knowing that it is promised. If all great Christmas songs capture some feeling deeply specific to the season, let it be said that this is the greatest example of the form: a song about desire, for a holiday about wanting.

This article originally appeared in the Dec. 23 issue of Billboard.