I have a BA in Film Studies, so I'm not sure if that's enough to call me an expert, but here's what I know.

-The actors sometimes had lines and they did speak them. Other times they didn't and were told to pantomime speech, as the interstitial cards might not have been written at filming. In fact, early silent films didn't have interstitial cards, but there'd be an in-house interpreter in the theater to explain the action to audiences. Short answer to that one: it varied.

-Music usually wasn't played, though sometimes the piece of music to be played with the film would be uniform throughout the country (sending the music notes to movie houses), and certain silent films had people playing music on set to help the actors get into the scene.

-Directors would yell cues and instructions during live takes quite often. Then like now, however, different directors had different styles of directing.