"I/O" (typeset as "i/o") is the fourth single and title track of English musician Peter Gabriel's tenth studio album I/O, his first album of original material since 2002's Up, and his first featuring a title track. Three versions of the song have been released: the "Bright-Side Mix" (mixed by Mark "Spike" Stent), the "Dark-Side Mix" (mixed by Tchad Blake), and the "In-Side Mix" (mixed by Hans-Martin Buff). The Bright-Side mix of "I/O" was released on the Pink Moon, the full moon in April, which occurred on the 6th. The Dark-Side and In-Side mixes followed on the 20th of April.