Changes planned for NBC's 'The Voice' this season

April 18, 2012: Reality series "The Voice" executive producer Mark Burnett (L-R), coaches CeeLo Green and Blake Shelton, and producer and host Carson Daly take part in a panel discussion at the NBC Universal Summer Press Day 2012 in Pasadena, California. (Reuters)

MALIBU, Calif. – NBC's "The Voice" is adding a bit of thievery to its format.

Executive producer Mark Burnett said Sunday that the singing contest will let coaches "steal" contestants from each other during the show's "battle rounds."

The show also will introduce a new "knockout round" to slice the number of contestants on each coach's team, Burnett told a Malibu, Calif., news conference. He was joined by coaches Christina Aguilera, Cee Lo Green, Adam Levine and Blake Shelton, and host Carson Daly.

They were promoting the series' third season, beginning Sept. 10 as "The Voice" adds a fall run to its original midseason slot.

Because the coaches have busy music careers, Burnett said, substitutes may be needed in future. But the original four have "chairs for life," he said.