The 1920 version 0f the famous novel by James Fenimore Cooper was not the first(a 1911film had that honor), but this one was deemed culturally significant in 1995 and was selected for preservation in the United States National Film Registry. it’s a beautifully filmed piece. I know little about silent films, but I presume the music score was added later. The only real reference I have is those old Beverly Hillbilly shows with the lady banging away on a piano. Not a reliable basis I would presume.
This version has less emphasis on Natty Bumpo, pushing him into the background, and concentrates on the love story between Cora(Barbara Bedford), Colonel Munro’s oldest daughter, and Uncas(Alan Roscoe, billed as Albert Roscoe), the Mohican.
We see a rather brutal slaughter of the fort and it’s inhabitants. Then the further betrayal of Magua(Wallace Beery) at the Delaware village, then taking of Cora as his wife. being allowed to leave unmolested. Uncas and Bumpo being stopped from bothering them for long enough to get a big lead.
Then Uncas pursues them, arriving along a cliff top in time to see Cora fall to her death, then gets into a fight with Magua, to be killed himself, then Bumpo killing the evil one with a shot. The film closes with the funerals of Cora and the last of the Mohicans.
The film was surprising to me with the dignity they treated the “mixed” relationship between Uncas and Cora. I’d always presumed sympathetic Indians came much later in the film 
world. Shows how little I really knew. Always glad to learn more about such things.
I found this one significant for one of the minor players. There was one actor, an unknown at the time, the picture to the left, who got no billing at all. He played one of the marauding Indians in the massacre of the fort and it’s people. Some young fellow named Boris Karloff. He can be seen tossing a baby up into the air about fifty minutes into the film. A link below to the film.
Some films definitely were distributed with scores for the local cinema orchestra to perform…while the smaller theaters were at least as likely to have an organ (and organist) as piano (and pianist). A whole lot of early film theaters were simply the local vaudeville theaters.
Whichever it was, the soundtrack on the video you provide is pretty nice, I wouldn’t mind having it on CD.