On second viewing I think something else was revealed... what the significance of "the Song" is: Earth 2! Hera said she was drawing the stars
. The Five heard music.
Starbuck was taught the music.
The music was heard by the Four when at the nebula, and the nebula was meant to point them to Earth. The song is the map, not to Earth 1, but Earth 2.
Perhaps by calculating the harmonic identities of those notes, one can find the stars they represent, and, from there find the habitable planet.