Among her many achievements, Reddy is best remembered for the 1972 hit 'I Am Woman,' which became the unofficial anthem of the women’s rights movement.
'Let's Get It On' became the second of Marvin's three US pop chart-toppers.
The movie will be released on September 11, with Reddy played by Australian film, TV and theater actress Tilda Cobham-Hervey.
For every anthem and romantic ballad, female artists have also asserted their independence through empowering lyrics, challenging the constraints of gender stereotypes, bad relationships or the music industry itself.
In remembrance of the much revered Grammy Award winner and member of the Roll and Roll Hall of Fame.