Clean

This chilling electronic tune finds Swift collaborating with one of her heroes, the British folktronica singer-songwriter Imogen Heap. She told The Sun: "We did a one take vocal and it was just so inspiring to see a woman do all the technical things in the studio that you usually see men do."

Imogen Heap is probably best known for her 2005 song "Hide And Seek," which was later sampled in Jason Derülo's #1 hit "Whatcha Say." Her 2009 album, Ellipse, earned Heap two Grammy nominations, winning Best Engineered Album, Non-Classical, in recognition of her own technical work on the record.

The lyrics are heavy on metaphors of drowning and addiction until Swift finds she is "finally clean" and ready to move on. She told The Sun: "It's about comparing getting over a relationship to sobriety; it has a lot of different references between addiction and moving on from a relationship."