I don't know who sings it but Aicha doesnt know what she is talking about. That song WAS in the movie. It may not be on the soundtrack but it was the song played at his little brother's funeral.
The title is We shall walk the streets of the city. I am trying to find a performer or choir of this song but it seems really hard on the net believe it or not. I will try my luck in a specialized music store for Gospel Choir, you need to seek the traditional version of it. Many imitation has been done but yet have not found the warmth and soul full version has heard in the movie Ray. I will keep you posted if you are still interested in founding that kind of version.
The song I remember is, We Will Walk Through The Streets Of The City.
Ray is the movie that was made on the life of the famous blues musician Ray Charles, in the year 2004. Most of the songs in the movie were by Ray Charles himself. However, the song that you have mentioned was not part of the movie. Here is a complete list of the songs played in the movie: