The Marble Index is the second solo album and third studio album by German musician Nico, which was released in November 1968 on Elektra Records. The avant-garde sound introduced in the album—a stark contrast with her folk pop debut, "Chelsea Girl"—was the result of the combination of Nico's droning harmonium and somber vocals, and producer John Cale's musical arrangements, which were inspired by modern European classical music. Nico envisioned the release as an attempt to get artistic legitimacy, thus also drastically changing the looks that had initially made her famous as a fashion model.