Two music genres that first became popular in the 1950s and 60s.
Reveal top + bottom answer and reasoning
Answer: ROCK SOUL
Top half: ROCK - ROCK is the first half of "rock soul", the top + bottom answer for the shared final clue: "Two music genres that first became popular in the 1950s and 60s."
Bottom half: SOUL - SOUL completes "rock soul", so the top and bottom rungs answer the shared final clue together: "Two music genres that first became popular in the 1950s and 60s."