"I Don't Know What It Is" is a song written and performed by Canadian-American singer-songwriter Rufus Wainwright. It was the first single from Wainwright's third studio album Want One and was released in a slim-line jewel case format on July 26, 2004.

In addition to the UK and Japanese versions of Want One, the song also appears on the bonus DVD that accompanies Want Two (Rufus Wainwright: Live at the Fillmore), All I Want (DVD), and Want, a repackaged UK double album that contains Want One and Want Two.

In All I Want, producer Marius de Vries admitted that "I Don't Know What It Is" was one of the most complex production challenges he had ever faced, with its hundreds of layers of separate orchestral, choral, and vocal parts. Between "running around" and "chugging along" "on a train going God knows where to" in a sort of aimless wander, transportation is a major theme of the song. Wainwright alludes to several locations, from precise ones such as Calais, Dover, Poland and Lower Manhattan to more abstract locales like Heaven, Hell, and Limbo.

Wainwright said the following of the song:

"When I first came up with the lines, I don't know what it is, but you got to do it/ I don't know where to go but you got to be there, I was at this party for The Strokes in New York. There was this prevailing sense of, 'We're not quite sure what's happening or what is cool, but we know that it's somewhere around here, in this room.' It was this vague confusion, with everybody kind of sniffing for blood. It wasn't that it was a bad party, or that I don't like The Strokes; I just think there's a lot of confusion right now in the music business. Then, later on, I realized the song was really personal. I didn't know where I was, and I didn't know I was actually lost. It wasn't about the party at all; it's about searching but not knowing what you're searching for. There's the train motif, being on this train heading for either oblivion or salvation and just holding on for dear life. That song came down from some mountain somewhere, because it was right after I wrote it that I sort of packed it in."

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Wikipedia