Jam Productions at 50: Arny Granat and Jerry Mickelson recall the gigs, twists and turns in Chicago’s rock ’n’ roll success story

CHICAGO — Once upon a time, there were two young men named Arny and Jerry who shared a dream and a passion for rock ’n’ roll, so they went about the risky business by founding what they would call Jam Productions and whether you know it or not, you know Jam.

If you have been to a concert or any of the thousands of other events and entertainments, mostly here but elsewhere too, over the last half-century, you have, in a real sense, been a guest of Jam.

You paid for these entertainments, of course, but it was Jam who made them possible.

This winter marked the 50th anniversary of the venerable company that has withstood competition both small (Cubby Bear) and large (Live Nation); dealt with performers demanding increasingly large financial guarantees,