New 'The Sing-Off' judge Sara Bareilles co-hosted the fourth hour of 'Today' (weekdays, 9AM ET on NBC) while Kathie Lee Gifford was off shooting her 'Hot in Cleveland' cameo. Bareilles, who's a sweetheart by nature, talked about the challenge of giving singers negative feedback, sang some a capella of her own and hoola-hooped with Hoda.

Bareilles struggled to figure out how to provide substantive criticism without coming off like a jerk. "It's hard to be critical sometimes. I see that now as I'm watching the show be aired, and I remember feeling self-conscious about wanting to point out places where they need to make improvements," she said.

Sara Bareilles, the woman responsible for 'Love Song' and most recently 'King of Anything,' has joined 'The Sing Off.'

"I'm extremely excited to be joining the panel of judges for 'The Sing-Off' this fall!" Bareilles said in a statement. "A cappella music is very near and dear to my heart, and I have been a huge fan of the show from the beginning. I love the opportunity to be a part of something that celebrates a genre of music that I just adore and believe in. I can't wait for it to start."