The simple answer is, that it doesn't matter. Singers cover their right ear when they sing because it's more comfortable for them. That's why most singers are right-handed - it just feels more natural to have the right hand free to move around and gesture while they're singing. But there's a more scientific reason why singers cover their right ear when they sing. Studies have shown that when we hear our own voice, it sounds different to us than when other people hear it. This is because the sound of our voice vibrates in our skull as it's produced, and we hear that vibration along with the air molecules that carry the sound to our ears.