I am happy to participate in a pronounciation audio recording session :)
Who knows. but I took this from wordreference:
hap•py (hap′ē), adj., -pi•er, -pi•est. delighted, pleased, or glad, as over a particular thing:
A reminder: "Mhysa" isn't High Valyrian. It's Old Ghiscari, the language of Old Ghis, the empire that ruled Slaver's Bay before the rise of the Valyrians.