A pretty good start to an interesting concept for a podcast.
Regarding your twin surprise at Susan's singing voice: I must say I've never heard anyone think Susan Alexander's singing "wasn't that bad!". To my ears--and those of everyone with whom I've ever seen the film--Susan's singing was obviously quite bad--at least by tough opera standards (and I know very little about opera!). Sure, maybe she's better than Roseanne on the mound, but Charles was 'forcing' a woman with sub-par skills to humiliate herself every night in front of people who knew exactly how far she was falling short. Even the 'working class' stagehands could tell how bad she was. It's the entire motivation for her suicide attempt...
And as a gear-head, I enjoyed your guest talking about Toland's camera. I've been to the ASC headquarters a few times for their occasional open-to-the-public lectures, and it's quite humbling to stand in the presence of that historic artifact!
I look forward to future episodes...