NOEL KING, HOST:
Good morning. I'm Noel King. A typical Yamaha DX7 synthesizer sells for less than $1,000. But this isn't any old DX7. It's the one Prince used on his 1984 album "Purple Rain." It's up for auction, and it is expected to bring in $25,000.
(SOUNDBITE OF SONG, "LET'S GO CRAZY")
PRINCE AND THE REVOLUTION: (Singing) Let's go crazy.
KING: The synth is a little scuffed up from touring, and it even has Prince's handwritten notes taped on top, notes like bass riff and dope drum. Transcript provided by NPR, Copyright NPR.