Smiles and Tears is the Eight Melodies of Earthbound.
Smiles and Tears appears in Mother 2 as the main song, and as part of the Mother 3 soundtrack, this time in the 16 Melodies.
There are eight parts to the song. Each part is found in one of the eight Your Sanctuary locations. They are:
The song is recorded in the Sound Stone. After the song is complete, Ness enters Magicant, defeats his Nightmare, and the power of the Earth fuses with Ness' own power, allowing him to defeat Giygas.