The personal touch of the pianist. Every pianist has their own style and story. When they cover 'Love Story', they pour their own emotions into it. Maybe they have a personal connection to the song, or they just want to convey a certain mood. This personal touch makes each piano cover unique. It could be the way they use dynamics, from soft and gentle to loud and passionate, that gives the cover its own character.
Sure. There are many talented pianists on YouTube who do amazing piano covers of 'Love Story'. For example, ThePianoGuys' version is quite popular. Their arrangement adds a unique touch to the song, with beautiful harmonies and a fresh take on the melody.
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.
It can be very atmospheric. In 'Angel Beats!', the piano music creates a sense of otherworldliness. The sad story is enhanced by the piano's ability to create a mood that is both dreamy and melancholic, making the viewers feel the characters' pain and unfulfilled desires.