Director Guy Ritchie used the soundtrack from the film The Dark Knight by Hans Zimmer as temporary music during editing. Zimmer was pleased when Ritchie asked him to do the score but was told to do something completely different. Zimmer described his score to Ritchie as the sound of The Pogues joining a Romanian orchestra. For the musical accompaniment, composer Hans Zimmer used a banjo, cimbalom, squeaky violins, a "broken pub piano" and other unconventional instruments such as the Experibass.
At first, Zimmer had his own piano detuned, but found that it just sounded out of tune. He asked his assistant to locate a broken piano. The first piano they located was passed over as it obviously had been loved and cared for, but the second one was the one they used in the production. Zimmer said "We rented 20th Century Fox’s underground car park one Sunday and did hideous things to a piano."