Well, Janis and Big Brother and the Holding Company. Joplin and the rock group she was a member of played two concerts on October 13th, 1968 at the Cincinnati Music Hall.
At the time of this show, Joplin and Big Brother were white hot. They were basking in the reception of their second album Cheap Thrills which became a smash (that’s probably why a second show was added). Here are a few concert posters and a live show via YouTube that was played the same year as the Cincinnati show (the video concert took place in San Jose, California) that should give you the feel of the Cincy event.

Image courtesy of concertarchives.org
Man. Don’t you just want to jump into a time machine?