This is the 8691st most frequent Japanese word.
旧知
"旧知" means "an old acquaintance" or "longtime friend."
In this sentence, 旧知 is used to refer to a person who has been known for a long time, emphasizing familiarity and past connection.
彼は私の旧知で、学生時代からの友人です。
He is an old acquaintance of mine and a friend since student days.
Here, 旧知 is metaphorically used for something familiar (the melody) that evokes sentimental feelings or nostalgia.
旧知のクラシック音楽の旋律が心に響きます。
The melody of classic music, an old acquaintance, resonates in my heart.
In this example, 旧知 refers to a prior familiar relationship between individuals that aids in their current interaction.