> REDACTED/source/The_Way_We_Were.ly:259:1: warning: cannot find > context to change to: Staff = lower
This is because you are already in the "lower" staff. As the name
`\change Staff` implies, it is intended to display material
temporarily in another staff. In other words, the eighth notes in
bars 19 and 20 should be entered in the "upper" staff, preceded with
`\change Staff = "lower"` and followed by `\change Staff = "upper"`.
Werner
