Mr. Koester was a pivotal figure in Chicago and beyond, releasing early efforts by Sun Ra, Anthony Braxton, Jimmy Dawkins, Magic Sam and numerous other jazz and blues musicians. He captured the sound of Chicago’s vibrant blues scene of the 1960s on records like “Hoodoo Man Blues,” a much admired album by the singer and harmonica player Junior Wells, featuring the guitarist Buddy Guy, that was recorded in 1965.
He founded the influential Chicago blues and jazz label Delmark Records and was also the proprietor of an equally influential record store where players and fans mingled as they sought out new and vintage sounds.
“Shakey Walter Horton and Ransom Knowling would hang out there, and Sunnyland Slim and Homesick James were always dropping by,” the harmonica player and bandleader Charlie Musselwhite, who was a clerk at the store in the mid-1960s, told The Times in 2009, rattling off the names of some fellow blues musicians. “You never knew what fascinating characters would wander in, so I always felt like I was in the eye of the storm there.”