On New Year's Eve my parents' friends would gather at our house and take risks, like drinking punch with real alcohol in it. Somewhere around 10 p.m. the kids would slink off and lie low until the effects of the punch kicked in, and everyone was too happy to remember that bedtime was long gone. When they began singing, we knew it was safe to come out from behind the sofa.

The round-faced, portly colleague of my father who had supposedly carried a gun for Hitler (though we never talked about this) became red and expansive and would lead the raggedy chorus in endless verses of nonsense songs about foreign people: The Swedes and the Irish figured prominently. Then the clock ticked down and everyone sobered up just enough to be sloppy and sentimental, and they sang the saddest song this 8-year-old had ever heard.

The Morgan Library in New York has devoted one little passageway in its oversize monument to American acquisitiveness to the Scottish poet Robert Burns and "Auld Lang Syne." There's a lesson in its small display of letters and music: that being old and belonging to a distant past are not the same things. The past is simply time that sneaked by while no one was noticing; but oldness, whether it's a photograph or a song that seems old, has a distinct smell and taste to it that good magicians can cook up in their workshops.

"Auld Lang Syne" smells old to me. I imagine it sung by firelight, in little stone houses that dot the gray and windswept coasts of northern Scotland. Beer--no, mead, if the Scots ever drank mead--is passed around. Old battles are recounted, the fear of death creeps around the room and everyone decides to take comfort in the illusion of hearty friendship. Then they sing it and big men blubber about things they won't remember distinctly in the morning. Now, that's life.

But that's an imagined past, not a real one. While rugged old men in kilts may have sat around getting boozy and singing songs similar to "Auld Lang Syne," the New Year's Eve standard that we know today didn't exist until the late 18th century. It's old, but it's not ancient. Even the association with champagne and midnight wasn't established until Guy Lombardo included it on a University of Virginia New Year's dance concert in the 1930s.

The song's genealogy is complicated. The famous words "for auld lang syne" (the Scottish Gaelic words--literally "old long since"--have the meaning "the good days long past") appear in earlier poems and songs, dating back at least till 1711. The Morgan Library has a complete song (from 1787) called "Auld Lang Syne" that begins "Should old acquaintance be forgot," but the rest of the words are very different and the melody bears no relationship to the one we know. Indeed, the earlier song has some ungainly rising intervals, the same problem that plagues "The Star-Spangled Banner." Its singability is questionable.

In the late 1790s, the Scottish poet and folklorist Burns enters the picture and further confuses things. Between 1796 and 1799, he crafts the words we sing today, and either composes, assembles or finds the tune we all know. Elements of the melody can be found in earlier songs, but not in the clean and simple and very direct form Burns used when the piece was first published in 1799.

Burns denied he had written the text or the music, though it's now believed that "Auld Lang Syne" is basically his own casserole cooked up from familiar materials. There was good precedent for this kind of reverse plagiarism. Thirty years earlier James MacPherson had fabricated entire epic poems and passed them off as the work of the legendary Gaelic poet Ossian. Samuel Johnson (among others) outed MacPherson as a creator, not a collector, but not before the poems had made most of Europe's young romantics even gloomier than normal. Burns, who did in fact collect real folk materials, was not quite so blatant, but he was insistent on downplaying his own role in the song's genesis.

Artists at the time were not particularly known for their modesty, so Burns's self-effacement is at first mysterious. As a Scotsman, he may have been motivated by nationalism, believing that his country needed a past more than he needed credit for a great song. But a letter included in the Morgan exhibit suggests that he was in search of an ideal during the time he wrote "Auld Lang Syne." He was clearly captivated by the theme of the poem's refrain, and especially drawn to the phonetic beauty of the title line.

When the piece finally appeared in finished form, the melody was accompanied by a running, chordal texture for the pianist's left hand, known as an Alberti bass (listen to Mozart's piano sonatas to sample this busy but dynamic style). By using what would have been a "high" accompaniment style--with its references to the European classical tradition--Burns gave the tune "respectable" treatment.

Throughout his life Burns was in search of an idealized past, and his creation of "Auld Lang Syne" was part of his quest. If you can't find a perfect marker of the olden days, then create one. Make it sound old, and sad, and far away.

We've completed what Burns began. Today, we've tossed aside the Alberti accompaniment--which sounds stodgy and over-sophisticated--replacing it with simple, open chords. A new sound has crept into the piece as well: the melancholy harmonic change at the very end of the verse (on the words "And days of auld lang syne"). It's a quick dash of what's known as the relative minor, the darker, sadder key that is twin to every major scale. The harmony appears briefly in the 1799 version, but is placed differently, and with much different effect. In contemporary harmonizations, its effect is modal, like a very old hymn, or the accompaniment of a primitive instrument, a sound our ears hear as wistful and somehow ancient. The melody has remained the same, but the accompaniment has been given the tea treatment, soaked in something dark that gives the appearance of age.

Years after my parents' parties, I began going to my own in New York City. Multiple divorces among the parents of my friends meant that there was always somebody's father's girlfriend who wasn't using her fabulous loft or penthouse for the evening. So we crashed and threw a party. At midnight, the singing began: "Auld Lang Syne" (the first verse only), and then whatever else we knew. We usually lapsed into TV theme songs--the only music we all had in common.

When "Auld Lang Syne" first appeared two centuries ago, the chorus was written for two voices, singing in close harmony. We don't sing in harmony much anymore, except for a few old holdouts at church. We sing "Auld Lang Syne" with the melody alone, as if the song has become a sign of our atomization and detachment, music for lonelier souls who sing primarily to themselves.