As children, Ida loves looking after her younger sister, Nora, but when their beloved father dies in 1926, everything changes. The two young girls move in with their grandmother who is particularly encouraging of Nora's musical talent. Nora eventually follows her dream of a brilliant musical career, while Ida takes a job as a nanny and their lives become quite separate.
The two sisters are reunited when Nora's life takes an unwelcome direction and she finds herself, embittered and resentful, isolated in the Tasmanian bush with a husband and children.
Ida longs passionately for a family and when she marries Len, a reliable and good man, she hopes to soon become a mother. Over time, it becomes clear that this is never likely to happen. In Ida's eyes, it seems that Nora possesses everything in life that could possibly matter yet she values none of it.
Set in rural Tasmania over a span of seventy years, the strengths and flaws of motherhood are revealed through the mercurial relationship of these two very different sisters. The Sisters' Song speaks of dreams, children and family, all entwined with a musical thread that binds them together.