Karmin's journey from YouTube novelty cover sensations to bona fide hitmakers continued this morning with a 'Good Morning America' performance of 'Brokenhearted,' the hit single from the group's debut album 'Hello,' which hits stores today.

Wearing a black floral blouse and bright yellow skirt, Amy Heidemann sang the poppy track while flashing her ever-present grin. Her fiance and bandmate Nick Noonan took his usual spot behind the keyboard and chimed in on vocals.

After the performance, the couple chatted about their music. Heidemann said she was shocked her covers of rap songs like Chris Brown's 'Look At Me Now' became popular. "I used to rap in the shower just for fun, cause it sounded good, but I never thought the rest of the world would appreciate it," she said. Noonan described the new album by saying, "There's a lot of big hip-hop drums, there's a lot of big choruses, and, of course, a little bit of rapping."

'Brokenhearted' is at No. 32 and rising after eight weeks on the pop chart. Karmin will continue their promotional push tomorrow with an appearance on 'Live with Kelly.'

Watch Karmin Perform 'Brokenhearted' on 'GMA'