This year, Summerfest had a knack for bringing legendary musicians together on stage. Stevie Wonder and John Legend over the weekend, Bob Dylan and Willie Nelson yet to come this week, and tonight, Chicago took the stage with Earth, Wind and Fire.

It was my first time to see either band; my familiarity stemming mainly from the mainstream inroads of classic songs like Earth, Wind and Fire's "September" and Chicago's "Saturday in the Park" managing to slip into the repertoires of underground DJs and in-house jukeboxes.

Those classic listens aside, both bands were relatively new to me tonight before seeing them live and in collaboration.

A free lawn show, the Marcus Amphitheater was full; the lower premium seats were full, aside from a few upper sections, and the lawn heavily sprinkled with listeners who had managed to score the free wristband.

Starting right on time, both Chicago and Earth, Wind and Fire took to the stage for an initial 30-minute collaboration. With nearly 20 musicians on stage, seven original members and more than 80 years of combined touring, the stage was littered with instrumental skill.

Summerfest isn't new for either of these bands. For Earth, Wind and Fire, tonight's show represented a Summerfest upgrade after playing to an overflow crowd last year on the M&I Classic Rock Stage. Likewise, Chicago is no newbie to the Summerfest scene; the band has played both the Marcus Amphitheater and side stages in the past.

And, this isn't the first time these two have toured together, either. Summerfest was just one stop on a 30 city-tour; the third tour Earth, Wind and Fire and Chicago have organized together.

The show opened with a rendition of Chicago's "Beginnings," followed by several Earth, Wind and Fire songs. Alternating between the two band's long lists of recorded classics, they covered nearly every era of their 40-year careers.

The remaining evening was split in half; Earth, Wind and Fire played first, followed by a set from Chicago and a collaborative close-out.

The differences in energy were obvious. Earth, Wind and Fire's intensity, specifically that of bass player Verdine White, consumed the crowd with exhilaration while Chicago seemed to go flat. Classic Chicago hits were met audience approval, but a piano solo and power ballad mid-set seemed weirdly out of place. Not knowing how to respond, a hefty portion of the crowd filed out.

Regardless of which band played, it was obvious the crowd favored the oldies. Classics like "September," "Saturday in the Park" and "Let's Groove" sent the audience to its feet with screams of applause.

Saucy as ever, the crowd reaffirmed the praise that has set Earth, Wind and Fire on stage everywhere from the Governor's Dinner hosted by President Obama in the White House to the U.S. Open within the last year.

But, if there was any redemption for Chicago, the last three songs of the night epitomized the modern presence of both Earth, Wind and Fire and Chicago. Playing potentially their three biggest hits, the 20 musicians on stage pumped out Chicago's "25 or 6 to 4," "Does Anybody Really Know What Time it Is?" and Earth Wind and Fire's "Shining Star." The crowd went wild for the guitar break out in "25 or 6 to 4," loved the saxophone battle and raved when they switched to the subtle funk of "Shining Star."