"Strain" is a little more out there, but does get used in classical music. I would not usually equate it to a whole song though, but instead a part of a piece.
Wow it was hard today. Was looking at it on and off all day, discussing it with others IRL, and never really got anywhere. Until suddenly just now, at quarter to midnight, the connection for blue jumped out at me and helped the rest of it fall into place.