A few years back my band did a a couple of gigs where we played some jazzed up versions of reggae songs and reggae versions of jazzy tracks. I had a couple of superb white female singers from a local folk band, whom i'd depped with on bass, to cover a couple of Wailers tracks that we were including from the twist of marley album by Lee Ritenour. One was no woman no cry and also Exodus. First one they were completely happy singing, but Exodus, they both felt the could't authentically identify with the context and message of the song and deliver it with the passion it deserves because of who they were. So they did all the other tracks and we had a black female singer to do Exodus. I totally accepted their feeling, the gig went down a storm.