In addition to the excellent discoveries that Nick has posted, I'd add this. Mahlon Bailey and James Duncan clearly knew each other from an early point. They were grammar school students together at Washington School and graduated together in January 1918 (Daily Times, Davenport, Jan. 24, 1918). Two years earlier, Mahlon Bailey hosted a Sunday school group, the Minute Boys, at his home. Bailey was elected president of the group; Duncan was elected secretary (Daily Times, Apr. 8, 1916).
Most importantly, in late January 1918, Bailey, Duncan, and Bix entered Davenport high school together as members of the mid-year freshman class, a class numbering 156 students. Duncan had elected the Latin Course; Bailey the Manual Training Course; and "Bix L. Beiderbecke" the Science Course (Davenport Democrat and Leader, Feb. 1, 1918). Undoubtedly they knew, or knew of, each other.
As for Duncan and the Linotype Company, I can't say for certain what he was doing there in 1920, but he is mentioned prominently in an article about the company's new location in 1920. 250 employees gathered for a housewarming party, and he is mentioned as tying for the prize for the "exhibition cake walk" (Daily Times, Davenport, May 1, 1920).
Finally, and this is important, Bix was not charged with a misdemeanor. It was a felony, a very serious offense that typically brought a three-year term in the penitentiary. A misdemeanor is a crime punishable by fine or a non-penitentiary term, typically a year or less. Most of the individuals convicted in Iowa of the statutory offense of lewd and lascivious acts on an underage person were sent up for three years.