"I (also) tried to gauge it on very calculated stuff, like 'Is there enough footage of people? Are there enough photos?'"
As with most projects of this sort, the filmmaker runs the risk of being hamstrung by the lack of surviving footage. In spite of a long career and dozens of local TV performances, the only footage of the Maddox Brothers and Rose known to exist today is a short silent color home movie from the mid-'50s.
And though Janis Martin made several appearances on "The Today Show," Jack Parr's "Tonight Show" and Ed Sullivan's series, no footage of Martin in her '50s heyday is known to exist today (though she is shown performing more recently at Great Britain's Hemsby festival).
On the other hand, vintage TV footage of both the Collins Kids and Wanda Jackson has survived to the present day.
"Obviously the Collinses were on TV every week for a really long time, and all that stuff's in good shape. But I fully expected that we would find (footage) of Janis. I was shocked when we couldn't find it."
A point made in the film is that when industry-manufactured singers like Bobby Rydell and Fabian started appearing around 1958, it was pretty much the end of rockabilly; particularly for the female rockabillies since the feeling in the industry was that girls didn't buy records by girls.
Which begs this question: If girls weren't the target audience for records by Jackson and other women, then who was? Horny teenaged boys?
"I've wondered about that a lot," says Harrington. "I'm not really sure what the answer is. It was the infancy of the modern record industry as we know it. Everyone was feeling their way through it. I mean, (Columbia) put Mitch Miller in charge of rock acts. I'm not sure they knew what they were going after."
"And that's why I think all those women had a-sides that were one tempo and b-sides that were another tempo. I think it's outstanding when you see a body of work like Janis Martin's, which is pretty straight-ahead (rockabilly. Chet Atkins) understood what she could do, and she got to do it."
"Whereas Wanda Jackson is kind of all over the map - really interesting recordings, but some of them are straight country and some of them are much more uptempo."
Although Harrington hasn't entirely decided on her next project, two possibilities that are closest to her heart include a film about the powerful Mexican border radio stations of the '30s and '40s as well as a documentary about the Carter Family.
The latter is of particular interest to Harrington since Roseanne Cash - whose stepmother June Carter Cash is Maybelle Carter's daughter - narrated "Welcome to the Club" and has discussed the project with Harrington.
"While I was making this film, I got connected with Roseanne Cash. And because I've been working on this film I came across so much stuff on Mother Maybelle, and the intersection between the Carters and Johnny Cash. And I started to think that it'd be nice to do a historical piece on the Carters and the Cashes. (Roseanne) e-mailed me one day and said, 'I just spent all this time with June and my father. People still get together and play on Saturday nights, and it'd be so great if you could make a documentary about this.'"
"And I said, 'Gee, it's funny you should mention it....'"
Photo of Janis Martin courtesy of Country Music Foundation