The members of Lady Antebellum welcomed a famous Josh on stage at Los Angeles' Wiltern Theater Thursday night (March 15). But it wasn't Josh Kelley, older brother of Lady A's Charles Kelley, whom Charles greeted in the audience. It was Josh Groban.

The classical pop superstar joined the trio for a gorgeous rendition of 'Hello World,' from the group's chart-topping second CD, 'Need You Now.'

Josh Groban's appearance -- and Lady Antebellum's obvious delight in performing with him -- was just one of the highlights of the 85-minute headlining show.

Coming onstage to Phoenix's rock hit, '1901,' the band opened with the up-tempo, crunchy 'Stars Tonight.' Only two singles into 'Need You Now,' Lady A already have enough hits to spread throughout the well-paced show. The trio followed 'Stars Tonight' with its breakthrough hit, 'Love Don't Live Here Anymore,' which highlights Charles' gruff, stellar vocals. Hilary Scott got her turn to lead next on 'Perfect Day' and their current No. 1, 'American Honey.' However, it is when Charles and Hilary sing together such as on 'When You Got a Good Thing' 'Lookin' for a Good Time' or 'Need You Now,' that Lady A soars. As their voices wrap around each other, with Dave Haywood chiming in on harmonies, the whole becomes much greater than the sum of its parts.

From the start, the band held the sold-out audience in the palm of its hand to a blinding degree. On 'All I Ever Need,' Charles, distracted by the adoring crowd, stumbled over the lyrics. At the song's conclusion, he laughed, adding, "I forgot to concentrate. We haven't had a crowd this loud in a long time. It's the first time in three years I've messed up the lyrics."

Despite the building stash of hits, Lady A still falls back on relying on a cover tune or two to stretch the show and give fans another instantly recognizable tune. In a move that showcased their winning vocals -- and in an homage to their recent shows at Nashville's historic Ryman Auditorium -- Hilary, Charles and Dave, surrounded by their band on acoustic instruments including upright bass, delved into Hank Williams' 'Lost Highway.' Perhaps as a sign of the times and a nod to the country act's growing pop appeal, the crowd responded much more warmly to Lady A's rollicking cover of John Mellencamp's 'R.O.C.K. in the U.S.A.,' interspersed with The Romantics' 'What I Like About You.'

.

The band turned to covers one more time to close its encore with The Beatles' 'Hey Jude.' They were joined by 'American Idol' season eight champ Kris Allen, who opened the evening with a brisk, energetic set. Like Lady A, he also ended his segment with a Beatles' song, the rollicking 'Come Together.'

While Charles may seem slightly more at ease than Hilary and Dave when it comes to continually glad-handing the audience, Lady A has come astonishingly far in a very short period to become a viable, truly entertaining stage act. While this date was a rare headlining gig, the band is on tour opening for Tim McGraw into August. And it's clear that they're ready to be the main attraction.