Definitely. 'The Grass Harp' falls under the category of short stories. It typically has a focused plot and limited characters compared to a full-length novel.
The Gate anime does cover the novels to a large extent. It takes the main plot elements from the novels, such as the opening of the gate to a fantasy world and the military's response. But there are some minor sub - plots and character developments in the novels that might not be fully explored in the anime due to time constraints or other reasons. Overall, if you've read the novels, you'll find the anime quite familiar, but it also has its own take on the story in some parts.
The 'the grass harp novel' mainly focuses on the unique charm of a particular community. It tells of the people's daily lives, their joys and sorrows. There are vivid descriptions of the local scenery which also plays an important role in the story, kind of like another character in the book. It also delves into themes of friendship, family, and growing up.
Well, in this story, it's quite important. Saul was often tormented by some sort of negative force. David's harp music was like a balm. It could ease Saul's troubled mind. It also shows David's special talent. He was not just a shepherd boy but had this gift that could reach the king. Through this, their relationship was initially formed, which later played a big part in the overall narrative of their story.
No. The Umineko anime does not cover the entire novel. There are a lot of details, plot developments, and character arcs in the novel that are either left out or not fully explored in the anime adaptation.