Iowa’s oldest and largest folk music festival gets underway tomorrow just south of Iowa City. The 30th annual Fiddler’s Picnic is a festival of traditional music featuring old-time fiddlers, folk instrumentalists and singers from across Iowa and several other states.Dennis Roseman is a math professor at the University of Iowa and is a member of the U-of-I Friends of Old-Time Music, which sponsors the event.Roseman says the festival is for people who just want to listen to the old tunes and for people who want to join in on dozens of impromptu jam sessions, either singing or playing an instrument.The festival runs from noon until 6 on Sunday at the Johnson County 4-H Fairgrounds.