The Spice Girls bandmates will officially release their cover of 'I Know Him So Well' on November 11.
The song - which will be available as a 2-track CD and digital bundle - appears on Melanie C's latest album Stages, which was released in September this year and entered at number 50 on the charts.
Discussing the duet with Digital Spy, she said: "I wasn't sure she would do it but when I asked her she squealed!
"It was so emotional when we first heard our voices together again. It's so Spice Girls. I'm so excited for people to hear it."
The track was originally released by Elaine Paige and Barbara Dixon in 1984 and was parodied last year by Susan Boyle and Peter Kay.
The star recently revealed that her Spice bandmates "laughed and cried" when watching the rehearsal for their upcoming musical Viva Forever.
Listen to 'I Know Him So Well' below: