This is the 920th most frequent Japanese word.
良く
"Well" or "often."
'良く' is used here to mean 'well' or 'clearly', describing the manner in which the music is heard, emphasizing clear and good perception.
音楽が良く聞こえます。
The music can be heard well.
'良く' is used here as an exclamation meaning 'well' or 'good', appreciating someone's actions or performance.
良くやった！
Well done!
'良く' is used here to mean 'often', expressing the frequency of his coming to the park.