It was about mid-way through the nostalgic ode "Old Days" Sunday night at the Riverside Theater that it occurred to me that Chicago's vast and popular jazz-rock-pop catalog has, in essence, served as life's soundtrack for almost anyone who came of age in the 70s and 80s.

An adoring, near capacity crowd agreed -- roaring their approval and singing along, word for word, with virtually every song as the band tore through hit after hit over the course of two solid hours of pulsating jazz / rock fusion.

It was a veritable sea of bobbing bald and graying heads -- each with a sparkle in their eyes and smiles on their faces elicited by classic songs that made us all feel like teens again.

It's been more than 40 years since Chicago Transit Authority burst onto the music scene with its brassy mixture of jazz / pop / rock and the band is one of only a few that remain from that era to have never broken up or taken an extended hiatus from recording or touring.

They've sold more than 120,000,000 million records, rank No. 13 on Billboard's Hot 100 All-Time Artists -- basically they're earned the right to rest on their laurels.

But you would never know that judging from the band's lively, energetic performance on Sunday. The band looked and sounded amazingly fit and genuinely seemed to be enjoying themselves and their craft -- maybe even more than ever before.

Led by original members Robert Lamm and Walt Parazaider, Chicago rolled out tunes spanning their entire career -- from "I'm a Man" to the title track of their latest release "Stone of Sisyphus" -- a non-stop a hit parade other artists could only dream of.

They wisely handled mid-career pop hits with enjoyable, upbeat medleys and prominently featured seemingly omnipresent songs like "Just You 'N Me," "Saturday In The Park," and "Alive Again." They even threw in a searing version of the big band standard "In The Mood" to overwhelming approval from the crowd.

By the time they got to the rousing closer "Feelin' Stronger Every Day" and encores "Free" and "25 or 6 to 4" - the Riverside crowd was as loud and lively as your typical Vans Warped Tour audience. Really.

Chicago is a band that has stood the test of time. Their songs and talent have weathered the storms of fad and fashion and the band remains as strong and vibrant a live act as I've seen in years. They made me -- and a whole bunch of other aging rockers feel like kids again on Sunday.

Here's the Chicago set list from Sunday Night:

Questions 67 And 68
Dialogue (Part I & II)
Make Me Smile
Colour My World
Stone Of Sisyphus
If You Leave Me Now
Call On Me
Alive Again
I Don't Want To Live Without Your Love
Look Away
You're Not Alone
Wake Up Sunshine
In The Mood
Hard Habit To Break
You're The Inspiration
Old Days
Beginnings
I'm A Man
Does Anybody Really Know What Time It Is?
Just You 'N' Me
Hard To Say I'm Sorry / Get Away
Saturday In The Park
Feelin' Stronger Every Day

Encore:
Free
25 OR 6 TO 4