“The music on Illinois (with its cover subtitle of Sufjan Stevens Invites You To: Come On Feel The Illinoise) encompasses folk, pop, classical, disco and Reichian minimalism. Stevens creates an orchestral effect using multi-tracking and his classical training allows him to employ baroque counterpoints and shifting time signatures. And he plays many of the instruments himself alongside a band, choir and string quartet.

However, on John Wayne Gacy, Jr. only piano and guitar accompany Stevens’ gentle, affecting voice. This song is about the notorious serial killer who terrorised the Chicago area from 1972 to 1975 and tortured and murdered at least 30 victims. It is a disturbing, controversial track: was Stevens showing sympathy for the devil?

The lyric describes a childhood incident which no doubt contributed to Gacy’s sadistic sociopathy. His mother was ‘folding John Wayne’s T-shirts when the swing set hit his head’ resulting in a blood clot in his brain. This changed Gacy from a child whom ‘the neighbours adored for his humour and his conversation’ to what he would become. ‘Twenty-seven people/ Even more, they were boys/ With their cars, summer jobs.’

The New York-based Stevens considers his religious beliefs to be a private matter and will not discuss them with the press. But his songs are suffused with Christian imagery. On John Wayne Gacy, Jr. he goes beyond trying to comprehend evil to actually empathising with a heinous killer. ‘And in my best behaviour/ I am really just like him/ Look beneath the floorboards [where Gacy hid his victims]/ For the secrets I have hid.’

This is a stunning observation about humanity’s capacity for cruelty and together with the song’s lovely, lyrical melody and tenderness of the vocal it is a moment of compassion and Christian love unlike anything else I have heard in contemporary popular music.”