A couple of aspects I found striking. First, do you know the lyrics of "Mocking Bird"? Until today, I'd never paid any attention to them beyond the eponymous chorus, although I've known the tune for most of my life--I think it figured on "Captain Kangaroo" when I was a tot, and I couldn't begin to guess how many times it's popped up in various contexts since (although, now that I think on it, not in more recent years; I guess it's become another of those "formerly common currency" cultural items). I'd always thought it was just a pretty, cheerful little late-19th-c. ditty. Wrong! Playing Alma's record at "Victor speed" (76 RPM, +/-), her enunciation was admirably clear, and I was astonished to discover the thing is about as maudlin as can be, cheerful tune notwithstanding. The singer is going on about a lost love buried down in the stereotypical valley, and that mocking bird is twittering away above her grave. Yikes!
Second, Alma Gluck was popular, but these two records give pretty striking evidence of just how popular: "Mockingbird" is a 10Q stamper, and that pales against "Aloha," which is a 22X! I've seen some big numbers along the line, but I don't remember seeing numbers that high on any other red seals of my acquaintance.