Like well-oiled gadgetry, Iowa City’s Family Folk Machine has found a way to switch gears, shifting rehearsals and concerts online. The final results will debut on YouTube at 3 p.m. Sunday.The intergenerational choir was in the midst of preparing its 2020 spring concert when the global pandemic brought that to a screeching halt.“It’s so weird to be at this anniversary,” said Jean Littlejohn, 49, of Iowa City, who founded the group in January 2013, conducts the choir and serves as the nonprofit organization’s executive and artistic director.