The song tells a story about a secret military plan to create a sound that is horrific enough to kill from a distance, much to their chagrin, as they were originally 'making music', and 'sounds that could thrill'. The ending of the story is unclear, but in the music video nearly every person working on the project is killed by the horrific sound, which is in the form of a grotesque monster.
"Experiment IV" was released on October 27 1986 and climbed to number 23 in the UK Singles Chart, alongside "Don't Give Up", Bush's duet with Peter Gabriel, which reached number 9. This made her the first British female to have two singles chart simultaneously on the UK Top 40.
An extended version of the song appeared on the 12" vinyl release of the single, which again included "Wuthering Heights (New Vocal)", her re-working of the song which catapulted her to stardom in 1978, together with "December Will Be Magic Again". It was also included as the last track on the second CD, second cassette or third LP of rarities on the This Woman's Work box set released in 1990.
The song is notable for featuring Nigel Kennedy on violin, who at one point replicates the screeching violins from Bernard Herrmann's famous scoring of the shower scene in Alfred Hitchcock's 1960 film Psycho.