The lunatic is in my head.Roger Waters wrote those lyrics for his former bandmate: "The lunatic was Syd, really. He was obviously in my mind." The line about the band playing different tunes could be interpreted several ways. Pink Floyd indeed played different tunes and changed their style after Barrett left, but it could also be about one of the symptoms of Barrett's mental illness and/or drug use -- he would literally play different songs from the rest of the band onstage.
The lunatic is in my head.
You raise the blade, you make the change,
You rearrange me till I'm sane.
You lock the door and throw away the key,
There's someone in my head but it's not me.
And if the cloud bursts, thunder in your ear,
You shout and no one seems to hear,
And if the band you're in starts playing different tunes,
I'll see you on the dark side of the moon.
And yes, I do realize there is a "Floyd" theme to my posts today.