When tybalt is ready to seize romeo and throw him out of the party, what does capulet say to tybalt? why? what is tybalt's reaction to this?

This, by his voice, should be a Montague. Fetch me my rapier, boy. What, dares the slave come hither, cover'd with an antic face,To fleer and scorn at our solemnity? Now, by the stock and honour of my kin, To strike him dead I hold it not a sin. 
Because Tybalt is a capulet and Romeo is a Montague and they are in a feud of families.
He states why he should kill Romeo

Just pretend that your talking to a empty room

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.