The Dixie Chicks have taped two episodes of Sesame Street. On the first, airing Feb. 25 on PBS stations, they sing "There's No Letter Better Than B" with Baby Bear, Bert, Big Bird, the Muppet Roosters and the Muppet Chickens. The second episode, airing Feb. 28, features the Dixie Chicks and the Muppet Chickens singing "Sing." 01/29/02