With "emotion" is subjective. To me, if I can predict what your next run is going to be, it implies an emphasis on formula over soul.
Mary, Aretha, Whitney, Al, the soul greats, you never knew where they were going. You'd think they were building up a slide to a blues note but they'll stick to the major scale.
Then they'll do an extended major passagio and out of nowhere drop into the blues or pentatonic scale, then jump back into major before you even realize they had left.
They ad-libbed from the heart, instead of just repeating the lyrics of the chorus they'll throw in a personal line other than the standard "oh baby" and "yeah baby" pop artists are known for. Very intricate things that make a performance come alive. They'd be doing a rock song but add a jazz scat, or a jazz song and belt in the 4/5th octave.
They can sing the same song 10 times and it would be completely different each time. I've seen dozens of youtube vids of Aretha doing Natural Woman live and it's NEVER had the same ending, the music is different, her runs are different.
Something tells me if I check Leona's live vids, they'll be good technical performances, but they'll be near-carbon copies of the recorded track. Even ones where she does change it up, it won't be anything drastic. An extra run here, a slide going down instead of up there. People with good ears can listen to hear and tell where she's going with moderate accuracy. There are so many pop songs I'll hear for the first time and sing along, matching the ad-libs because they're basic from the attack, the passages, even the wording sometimes. Chances are there's going to be an "ooh baby" or "yeah girl."
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