Answer:
main idea or the expression
Explanation:
Theme is the main idea or the expression of the author about the context of the song. It is the central idea around which the entire story revolves.
Theme also gives a indication of the background of the write up or the intention of the author.
True! Although it does not contain any original work, it cites all the sources that it has gotten it's information from, so it is true that it is not an example for plagiarism.