Q: Context: "You've Lost That Lovin' Feelin"' is a song written by Phil Spector, Barry Mann, and Cynthia Weil. It was first recorded by the Righteous Brothers in 1964, produced by Phil Spector. Their recording is considered by some music critics to be the ultimate expression and illustration of Spector's "Wall of Sound" recording technique. It has also been described by various music writers as "one of the best records ever made" and "the ultimate pop record".

Question: who sang the original you've lost that loving feeling?
Let's give stream of consciousness below
To answer this question, we should know that: It was first recorded by the Righteous Brothers in 1964, produced by Phil Spector. So the answer is the Righteous Brothers.