"The Hardest Thing To Do" evokes early '80s Fleetwood Mac and other golden Los Angeles pop, floating along with help from a sturdy bass line and crude, flat percussion. It's the work of Robyn and Metronomy's lead singer, Joseph Mount. The collaboration displays a different side of Robyn, who has been mostly associated with anthemic, pulsing club tracks in the '00s.
The song appears in the movie Partisan alongside a score by Oneohtrix Point Never. Jarvis Cocker and Sébastien Tellier also contributed to the soundtrack under assumed names. Watch the action-packed clip for Robyn's track above.