This is from the ACM awards show that is Carrie Underwood and Miranda Lambert singing and telling about their new songs. This just happened and the . Miranda Lambert pops in as a surprise guest during Carrie Underwoods Party for a Cause performance. For more from the ACM Party For A Cause Festival . Carrie Underwood, Miranda Lambert, Katy Perry, Dolly Parton, Brittany Kerr, Luke Bryan, Carolyn Boyer, Nicole Kidman, and Keith Urban make our best dressed . This is from the ACM awards show that is Carrie Underwood and Miranda Lambert singing and telling about their new songs. This just happened and the .