"Dear Diary" is a 1969 song by the progressive rock band The Moody Blues. Written by the band's flautist Ray Thomas, "Dear Diary" was first released on the 1969 album On the Threshold of a Dream.

The lyrics of "Dear Diary" draw inspiration from the Eastern concept of Maya (illusion), and basically describe a man's alienation from the illusions of normal society. He sees people "rushing around so senselessly" and posits that "if they weren't so blind, then surely they'd see, there's a much better way for them to be." In the bridge of the song, the narrator states:

"They don't know what they're playing, They've no way of knowing what the game is, Still they carry on, doing what they can."

The song itself has a slow, ethereal sound to it, and Ray Thomas's lead vocal track is run through a Leslie speaker for an eerie effect. In a moment of humor typical of Thomas's writing, the song ends with the narrator remarking that someone had exploded an H bomb, but not anyone he knew.

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