Hang the DJ

According to Annabel Jones, the series' co-creator, "Hang the DJ" was intended to reflect on the state of dating in the present day and the "general sense of loneliness".[6] The script for the episode was rushed because of its deadline at a busy point in the production cycle.[7]

The first idea for the episode was conceived by series creator and episode writer Charlie Brooker, who conceived of the Coach dating app by analogy with the audio streaming platform Spotify: it determines a "playlist" of relationships that one should have before settling down with a partner.[7][8] It was not obvious what storyline could be developed when the dating app users' experience was predetermined. According to executive producer Annabel Jones, variations upon the idea were considered over several months. The idea was conceived that the app could learn from each relationship. Amy and Frank being driven apart before reuniting was a desired narrative arc, which was able to be fulfilled when the twist of the episode was introduced.[7]

The episode can be seen as a "companion piece" to series three episode "San Junipero", as they have positive tones, in contrast to other Black Mirror episodes. Brooker was concerned about fans disliking the "light and playful comic tone" of the episode and he was initially reluctant to write a happy ending. However, he expected that people would enjoy Amy and Frank's relationship, having seen positive audience reaction to Kelly and Yorkie in "San Junipero". Both episodes reveal in a plot twist that the setting is a simulated reality.[7] One challenge with "Hang the DJ" was to keep this twist unclear until the very end while still providing enough detail to make the viewer aware that the setting is unusual.[6] In one scene, Frank and Amy suggest that the world is simulated, as a "double-bluff" from Brooker.[7]

Another the writers discussed was how long to have the semi-permanent relationship between Amy and Frank last. Brooker said their ultimate decision of five years is "a reasonable amount of time for a serious relationship", but Frank is disappointed to discover this as it means the relationship will end.[9] Frank observing the relationship time caused a structural issue in the script, but the scene was seen as important and so the script was reworked around this idea.[7]

The idea that the "experiment" of the simulation would be run 1000 times simultaneously was one first considered for previous episode "White Christmas". In the episode, a simulated copy of a person confesses to a crime. A person asked whether this would be admissible evidence, to which Brooker replied that the simulation could be repeated, but with the person in a different setting each time, to increase reliability.[7]

American director Tim Van Patten directed the episode. Georgina Campbell was cast as Amy and Joe Cole was cast as Frank. The pair did a chemistry test before filming, to check they could build a rapport. Campbell found Amy to be "full to the brim with hope", with a "nervous excitement" about dating.[7]

The setting was based on Soho Farmhouse in Oxfordshire, an expensive holiday area where production designer Joel Collins had visited for a birthday party. Collins described that an "electric milk float" transports people around their cabins and the various clubs and bars. After Collins described this to Brooker, the setting was rewritten—having previously been drafted as tower blocks—to resemble Soho Farmhouse, or a holiday village owned by Center Parcs. The geometric design of the world was Collins' idea, intended to resemble the inside of a mobile phone—where various copper and brass lines are arranged on a green plate. Hexagonal patterns and repeated design motifs are used in the scenery as the setting is an algorithmic simulated world.[7] The interface for the Coach app was first designed by Erica McEwan, a member of the graphics department of the production. Further development and animation was undertaken by Painting Practice.[7]

Some exterior filming took place at Painshill, including the Pairing Day ceremony at a folly in the form of a ruined abbey.

Some exterior filming took place at Painshill, an eighteenth-century landscape park in Surrey. One of the original remaining structures, a folly in the form of a ruined abbey, served as the backdrop for the Pairing Day ceremony scene.[10] In this scene, Amy was to kick Frank, but Campbell's fake kicks looked unrealistic. Van Patten told Campbell to kick Cole for real and she accidentally kicked him hard enough for him to bleed—this was the shot that was used in the episode.[7]

The plot twist is revealed in a scene where the simulated world disassembles pixel by pixel to be replaced by one thousand copies of Frank and Amy in a black void. This was only described vaguely in the script, so the production took inspiration from 2013 science fiction film Under the Skin, according to producer Nick Pitt. The cast were confused about the intention during filming for this ending, particularly the footage taken against green screens of characters looking "meaningfully into the middle distance". When showing initial cuts of the episode to their partners, Jones and Brooker found that they did not understand the ending. To establish that the episode's setting had been a simulation, disembodied voice and text reveal that Amy and Frank had "rebelled" 998 out of 1000 times, leading to a 99.8% match for the pair, and dialogue in the previous restaurant scene was simplified. Additionally, visual effects developments led to characters "dematerialising" by a "graceful leaving of their body" rather than "being broken, squashed or incinerated", according to Pitt.[7]

The instrumental soundtrack for "Hang the DJ" was created by Alex Somers, with two pieces contributed by Sigur Rós.[11]

In May 2017, a Reddit post unofficially announced the names and directors of the six episodes in series 4 of Black Mirror.[12] The first trailer for the series was released by Netflix on 25 August 2017, and contained the six episode titles.[13][14]

Beginning on 24 November 2017, Netflix published a series of posters and trailers for the fourth series of the show, referred to as the "13 Days of Black Mirror".[15] On 6 December, Netflix published a trailer featuring an amalgamation of scenes from the fourth series, which announced that the series would be released on 29 December.[16]