https://en.wikipedia.org/wiki/Drake%E2%80%93Kendrick_Lamar_feud

A volley occurs when the other person responds, so if two songs are made before then, it still counts as a single volley.

Market extends until they stop responding to each other, by my judgement.

Here is how i am counting them so far

1 - Like That (Kendrick)

2 - Push Ups & Taylor Made Freestyle (Drake)

3 - Euphoria & 6:16 in LA (Kendrick)

4 - Family Matters (Drake)

5 - Meet the Grahams & Not Like Us (Kendrick)

6 - The Heart Part 6 (Drake)

7 - ???