If an artist wanted to create a relief in which a tree appeared further away than a park bench, carving the park bench more deeply (in high relief) would achieve this effect.

The statement is true. By definition relief in sculpting refers to the elements that are placed on top of a flat surface. Things that are "low" only stand lightly out from the background making it seem as if they are part of the background while those in "high" are carved further from the background making them seem like they are on top of the background. 

The gregorian chant was a major cultural milestone in the middle ages. it was one of the first codified forms of music meant to be played as written, where previously it was difficult to mass-produce and disseminate any music. what's more, these chants were also some of the first examples of musical notation: the notes and bars of today's music sheets are a reflection of centuries of evolution beginning with these chants. it became official throughout the entirety of the catholic church, meaning that nearly all of europe followed this musical notation and styling.