Demi Lovato Introduces Surprise Guest Brad Paisley at Summer Concert Series

— -- With a platinum song and new upcoming tour, Demi Lovato has a lot to celebrate.

The singer-songwriter rocked the "Good Morning America” Summer Concert Series in Central Park this morning, performing her hit songs "Cool for the Summer" and "Confident," which just went platinum.

Lovato, 23, is also enthusiastic about teaming up with pal Nick Jonas, as they launch their upcoming "Future Now" tour, she said.

"I think we're both most excited to see our fans and be able to perform," Lovato told “GMA” co-anchor Lara Spencer. "We toured together before several years ago and so, we've done this before and now we get to do it again ... we work really well together and we're business partners together. We own a label called 'Safe House Records,' so it makes a lot of sense."

Another star with whom Lovato is collaborating is country superstar Brad Paisley, whom she brought on stage this morning as a surprise guest, singing their new song "Stone Cold."

"I'm enjoying the country thing so much that I might put a little on my next album," Lovato said.

Paisley chimed in: "She's from Dallas, so she's born with it."