With a sparse stage setup, and deft, soulful musicianship, a Justin Bieber concert it was not. Then again, folks who packed Mohegan Sun Arena to see the Doobie Brothers and Chicago July 7 were there for the music, not the spectacle.

And fans got what they came for.

The Doobie Brothers kicked off the festivities in Uncasville. The band, best known for their lush vocal harmonies, is anchored by founding members guitarists/vocalists Tom Johnston and Patrick Simmons.

Highlights of the Doobie Brothers’ hour-long set included their hits “Jesus Is Just Alright”, “Black Water” and “China Grove.” Also, the group played three tunes from their forthcoming album.

Johnston’s and Simmons’ voices were strong, and time has done little to wilt their guitar playing.

Members of the Vocal Group Hall of Fame, the Doobie Brothers have sold more than 30 million albums since their formation in 1970.

However, like Chicago, these days, the Doobie Brothers are without, arguably, their best known singer.

Former bandmate, vocalist/keyboard player Michael McDonald tried his luck as a solo artist when the Doobie Brothers parted ways in 1982. The band would reform five years later, but McDonald stayed focused on his solo projects.

The Doobie Brothers have toured regularly and have returned to the studio sporadically since reuniting in 1987. The group’s latest effort is due out in September.

After a short intermission, Chicago took the stage at Mohegan Sun Arena. The band’s lineup includes founding members: keyboard player/vocalist Robert Lamm, trombone player James Pankow, trumpet player Lee Loughnane and Walter Pazazaider, on woodwinds.

With their trademark horn section taking center stage, Chicago churned out head-bobbers such as “Make Me Smile”, “Beginnings” and “I’m a Man” during their 90-minute performance, and mellow stuff like “Color My World”, “Hard Habit to Break” and “You’re the Inspiration.”

Chicago’s playing was excellent, but without a full-time lead singer on their roster, vocal duties were passed around the stage, which, at times, made it difficult to figure out whose voice was coming through the speakers.

Formed in 1967, Chicago has produced 11 No. 1 singles and sold more than 100 million albums. Their popularity has waned since the 80s, but the group maintains a rigorous tour schedule, while still producing new music.

Chicago’s most recognizable voices, Terry Kath and Peter Cetera, can only be heard on the band’s old records, however. Vocalist/guitar player Kath died of an accidental gunshot wound in 1978, and in 1985, vocalist/bass player Cetera left the band to concentrate on his solo career.

The Doobie Brothers’ and Chicago’s lineup looks a lot different than it did during the bands’ heyday, but fans at Mohegan Sun Arena didn’t seem to mind.

By the time the Doobie Brothers and Chicago performed alongside eachother following their individual sets, the crowd was revved up and dancing. With 17 musicians roaming the stage, the guys teamed up to perform the Doobie Brothers’ “Rocking Down the Highway”, “Taking it to the Streets” and “Listen to the Music” and Chicago’s “Does Anybody Really Know What Time It Is?”, “Free” and “25 or 6 to 4”, which capped the show.

Both the Doobie Brothers and Chicago appeared to have genuinely enjoyed themselves that night. Band memebers were playful with one another, and interacted with the audience. Smiles were abundant on stage.

To be so upbeat and energized after four decades in the fickle and, often times, brutal music industry is pretty amazing.