Ossia

Ossia (meaning "or" or "alternatively") marks a small-staffStaffThe set of five horizontal lines and four spaces on which musical notes are written.View full entry → alternative to the main musical text, typically offering a simplified version of a technically demanding passage or presenting the composer's alternative reading. It appears most frequently in virtuosic pianoPianoSoft, quietView full entry → and vocal music, where the main text may contain passages that are beyond some performers' capabilities.