Question

What type of word relationship does this analogy show?
cave:cavern::song:tune

Answer 1

I would say that these words relate to each other through similarity/same thing, different name. 

Answer 2

Sub heading - main heading analogy

Step-by-step explanation:

An analogy shows the relationship between two things at some point of similarity. The given analogy can be referred to the sub-heading-main heading analogy. In the given example, cave is a smaller section of a cavern and a song is a smaller part of a tune. Therefore, one is the bigger part and the other is the smaller part.