Hey, let's watch one of my favorite musical movie moments. Here from The Harvey Girls (1946) is "On the Atchison, Topeka and the Santa Fe." It's a big, overproduced ode to a railroad line performed by Judy Garland, Ray Bolger, Marjorie Main, Virginia O'Brien and anyone else who set foot on the MGM lot that week, even though they didn't film most or maybe any of this on the lot. Note that from the 4:50 minutes mark in this clip through the moment when the conductor shouts "All aboard!," this is one continuous take of two minutes and twenty-five seconds during which Ms. Garland and a whole lot of people hit their marks at precisely the right moment. Pretty impressive, I think…