According to an interview I recently read, Jeff Tweedy, singer, songwriter, poet and frontman for Wilco, has done a whole lot of listening to a CD called "The Conet Project," recordings of so-called "Numbers Stations." The title of one of the band’s albums (Yankee Hotel Foxtrot), and a good deal of its sonic landscape were inspired by the recordings. Take a look at www.irdial.com/conet.htm for more information about Numbers Stations and the CDs. (Below is some of the text off their site.) However, given that the CD set sells for $244.88 on Amazon, you might also just want to listen to a few MP3s from it at http://mirror33.archive.org/2/ird059/. Spooky and fascinating.

"For more than 30 years the Shortwave radio spectrum has been used by the worlds intelligence agencies to transmit secret messages. These messages are transmitted by hundreds of ‘Numbers Stations’….Shortwave Numbers Stations are a perfect method of anonymous, one way communication. Spies located anywhere in the world can be communicated to by their masters via small, locally available, and unmodified Shortwave receivers. The encryption system used by Numbers Stations, known as a ‘one time pad’ is unbreakable."