"When I got to Bletchley, it was like going to a music college."

Conductor, broadcaster, writer and TV/radio producer Bernard Keeffe talks about his wartime cipher decoding work at Bletchley Park, the musicians he met there (Daniel Jones (Under Milk Wood), Herbert Murrill, Wilfred Dunwell) and a Bletchley production of Ralph Vaughan Williams's Mass in G Minor, recorded by Alec Robertson:

http://www.sendspace.com/file/ub6l8t

(fragment from Feedback, 20 July 2007, BBC Radio 4)

But surely, music and mathematics have always existed side by side, the siamese twins of reason and emotion?

I've always loved music but loathed mathematics, because I'm the  mathematical equivalent of 'tone deaf ('innumerate'?). I am however deeply appreciative of the achievements of Alan Turing and his colleagues.

Just before the Great War started, the German Spy Ring used invisible ink for concealing secret letters in musical scores:

http://www.mi5.gov.uk/output/Page236.html

The invisible ink story reminds us of two other secret agents employing sheet music to hide their messages. Special Agent Gustav Mahler of the Austrian Geheimdienst was despatched in the early years of the 20th century to gather intelligence in the United States. Not finding any he returned home, but commenced a programme of encoding information in his own works. One of his final messages before he was neutralised with the aid of a bacterial weapon of unknown provenance reads in part "Du allein weißt, was es bedeutet... Leb wol, mein Saitenspiel... Leb wol leb wol Almschi". Here the reference to an unknown 'string game' is clearly a code, perhaps referring to advanced techniques for mind control at a distance, but the rest of the message remains obscure.

Agent Comrade Dmitri Shostakovich was also engaged in encoding messages in his scores but appears to have been at the very least a double agent. After his death several groups of insurgents, counter-insurgents and counter-counter-insurgents broke into bitter and acrimonious fighting over the contents of Shostakovich's encoded messages, each group claiming the messages were intended for them. On questioning, no two groups could agree on the content of the messages or even how and where exactly they had been encoded, although each individual agent claimed the messages to be perfectly intelligible, some even denying that they were in code at all. Several reputable and disreputable musicologists had to be kept under custodial supervision for extended periods for their own safety. It seems Comrade Shostakovich had the last laugh.

Who are these cryptic 'fallists' of whom you speak?

You're welcome, Mr Grew.

Elizabeth Poston is a new name to me. I haven't found much about the encoded messages in her music so far. I saw somewhere that Radio 4 made a programme about it.