What's the name of the violin score played by Shaiapouf when Meruem is born?
In episode 91 The Strong × And × The Weak, King Meruem is born. After his birth, he goes to the top of the ant hill where Shaiapouf plays a song titled In the Palace ~ Lamentoso.

This particular song can be found on the Hunter × Hunter (2011) Original Soundtrack 3 as track number 10.