While perhaps there could have been an official score I wouldn't be surprised if the pianist just played whatever the hell they wanted to play. Even up to the 60's you had projectionists remixing movies, as I recall the director of Bonnie & Clide once commented how he went to see his movie in a theater and the sound levels were all off. He went to see the projectionist who very proudly said he "fixed" the movie's "terrible" sound just like he did before with Shane, a movie whom the director had designed his sound around originally. It's also worth noting that theaters had the tools to do their own edits of the films into the late 60's, probably even after that. Studios could and would send information of recuts to theaters. Kubrick did this with 2001 because he made changes after the theatrical releases were shipped out. When DVDs come out with found "trims" these are often from theater basements where projectionists originally did it themselves. This is why there are often so many different versions of silent films, most were recut by theater owners. Either to change the length to have more showings or just to match the sensibilities of the theater owners. Theater owners often changed the framerate on silent movies as well for the same reason. Since it'd be much easier for a pianist to do impromptu both because they're live and because the songs they know by heart are easier than reading song sheets, it's not hard to imagine that happening.