"Chicago, April 1920" is the name of the first half of the double-length episode Young Indiana Jones and the Mystery of the Blues. While Mystery of the Blues was broadcast as a single episode in the United States and several other countries, it was separated into two one-hour episodes for broadcast in the United Kingdom: Chicago, April 1920" and "Chicago, May 1920".
The bookend clips for "Chicago, April 1920" included scenes of Old Indy (played by George Hall) with his grandson, Spike, an aspiring rock musician. Disturbed by Spike's music upstairs, Indy tells Spike that playing one song well is better than lots of songs poorly, and then recounts his experience with Sidney Bechet and jazz. In the end, Indy lets Spike practice in order to get good.
For information on the plot, cast and characters of the main part of the episode, refer to Young Indiana Jones and the Mystery of the Blues: Chicago, April 1920