"Moon" is a song by Icelandic artist Björk. It is the first track on her album Biophilia and was released as the fourth and final single before the release of the album. Each song in the album features a theme related to nature. In "Moon", Björk explores the lunar cycles and the effect they have on Earth.

The song "Moon" is based on four different sequences played by four different harpists: Zeena Parkins, Shelley Burgon, Sara Cutler, Carol Emanuel. These sequences repeat throughout the song, resembling the lunar cycles. The song has 17/8 time signature. The lyrics to "Moon" deals with themes such as rebirth, start over and mythology, making reference to the Moon as "adrenalin pearls placed in the gods' mouths".

About the song, Björk explained: "With each new moon we complete a cycle and are offered renewal —to take risks, to connect with other people, to love, to give. The symbolism of the moon as the realm of imagination, melancholy, and regeneration is expressed in the song"

The video for "Moon" was directed by Björk, M/M Paris, Inez & Vinoodh and James Merry and recorded spontaneously during the photo sessions for Biophilia. Björk sings the song with the orange crystal that also features on the Biophilia album and singles cover, in one take. Images from the 'Moon' app appear superposed throughout the video.

The 'Moon' app for iPad and iPhone was developed by 18-year-old programmer Max Weisel, and is a musical sequencer which features 17 moons (representing each pulse of a time bar in the song). By changing the position of each moon, one changes the note it produces, thus forming a new melody each time which can be played with Björk's voice. The app also allows one to play the original song.

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Wikipedia