I spent a few hours searching a German site called jpc - music a la carte. One of the discs I ordered (which may never come, as it may no longer be available - we shall see) is by Berthe Slyva, a French singer. This particular disc contained two vintage recordings of two songs from Prix de beauté, the 1930 French film which starred Brooks. The songs, "Je n'ai qu'un amour c'est toi" (the familiar closing song) and "Mais quand le coeur dit oui," both ended up on sheet music associated with the film. [ Another CD I came across on another website, featuring French recordings from 1930, includes another version of "Je n'ai qu'un amour c'est toi," this one by Marthe Coiffier. Check the box next to her name and then double click on the "Lancer L'ecoute" button to hear a 45 second sample!] I don't feel that either version of "Je n'ai qu'un amour c'est toi" on these two discs is the version heard in the film, so there is a third recording out there somewhere. (And no, it's not Edith Piaf.) This third version (by Helene Caron) may be the one issued as a 78 record in France around 1930.
My search around jpc also turned up a remarkable disc of German film music dating from 1900 through 1945. This album, Filmmuseum Berlin - Musik zum deutschen Film Vol. 1, contains all kinds of unusual recordings such as the "Caligari-Foxtrott" and music fromNosferatu and Metropolis and Pandora's Box! From what I can tell, some of these recordings are vintage, and some are contemporary. I will find out more when and if my order comes. (More info on this recording here - as well as sound samples.)
I also purchased a CD called TanzSzene Berlin 1930, a collection of vintage dance music which includes Ilja Livschakoff's "Du bist meine Greta Garbo," as well as a disc by Will Meisel which contains his classic " Dort tanzt Lulu." Another disc had a Pola Negri track . . . .