Music; a newbie question
I've started watching silent movies recently, and I've noticed something which I don't understand. When I look at two different videos of the same silent movie, often they'll have completely different soundtracks. And I've even seen some where the credits include an acknowledgement of a modern score, composed by so-and-so and performed by whoever.
Now, I'm well aware that the early silent films are all long since public domain, and that anyone can do whatever they like with them, including putting a new soundtrack on them. I don't mind that, but I would like to know whether what I'm seeing and hearing is close to what the original filmmakers intended. So, my question ...
For the typical silent movie, what was it that determined what the audience heard when they watched it? Was actual written music distributed with the movie? Or were there more general instructions without specific music, something like, "light and happy music for scene 23; solemn music for scene 24"? Or were the theaters given no guidance at all and expected to do whatever they liked?