The track by 35-year-old Blacc, whose real name is Egbert Nathaniel Dawkins III, pays homage to the chorus melody of Elton John's first UK top 10 single "Your Song".
Blacc made his UK charts debut in 2011 with "I Need Dollar", which peaked at number two, and last summer provided guest vocals for Avicii's chart-topping track "Wake Me Up", the Official Charts Company said.
John Legend's "All Of Me" climbed three places to take the number two spot, while Duke Dumont's "I Got U" featuring Jax Jones was down one in third place.
In the album chart, the Kaiser Chiefs went straight in at number one with their fifth album "Education, Education, Education & War", knocking winner of reality show The X Factor Sam Bailey's "The Power Of Love" into second place.
George Michael's former number one album "Symphonica" slipped one place to number three, the Official Charts Company said.