An analogy draws a relationship between two different things. The purpose is to compare those things by finding something that connects them, despite the differences. The question we are answering here provided us with the following:
tunnel:cave::note:song
Both pairs offer the same analogy, which is the part/whole one. A tunnel is a part of a cave. A big cave is usually constituted of several tunnels. The same goes for a note. It is a part of a song. A song is constituted of several notes. Thus, tunnel and tone are parts, cave and song are the whole.
