I listen to a lot of radio plays, and many times music is used within them that intrigues me and makes me want to find out what it is. More often than not, I am unsuccessful in doing this despite diligent internet searches and browsing through the BBC Radio 4 comment boards.
One piece has been nagging at me ever since I first heard it used in the BBC Radio 4 adaptation of John Le Carre's "Tinker Tailor Soldier Spy". It was a haunting circular theme for string quartet and it was effectively used to crank up the tension at apt points in the excellent production.
If I had thought about it properly, I would have deduced the obvious answer months ago, but it was only last week when I decided to listen again to the complete string quartets of Shostakovich that the question was solved.
Here it is, the 'lento' from the 7th String Quartet. The theme used in the play opens this movement.