Examples of Awesome Music in Visual Novels.
There is some debate as to whether Visual Novels are actually 'video games' or not. Nevertheless, Visual Novels do tend to have some great music which is sad since many people tend to overlook visual novels for other media.
(Note: If you come across any examples that belong to suspended/terminated Youtube channels, please remove them and if possible replace them.)
Youkai no Senritsu, used in the fandisc at the sad moments too, especially at the end of Houzuki's chapter.
Gentle Jena, the title screen from the very short VN Planetarian. Planetarian was made by KEY, most notable for making Air, Kanon, and Clannad so listening to this (peaceful) song can help you guess what kind of plot stuff will happen since it IS a KEY work.
Even though it's not in the music gallery of the game, the song that plays when you decide to "Play with Masato" is incredibly fun and catchy, even you can't resist the Muscle Sensation!
Let's Return for moments when you can look forward to a brighter day.
On the flip side A world where nothing happened, you hear this music playing and the static in the song starts to set in, and you know that mysterious, creepy, and possibly disturbing things await you.
You know that there are fun and exciting things awaiting you with Alicemagic.
Song for Friends is a bit sad but you feel you know that there is a ray of hope shining in front of you.
You found a closed world where only Regret and depression await you, sorry.
Final Ending is Little Busters!~Little Jumper ver.~, almost the same song as the opening, but with a change in lyrics and some musical instruments that make it feel nostalgic, hopeful, and there is a brand new exiting world out there for you to jump into.
Skyclad Observer from Steins;Gate. They even used it as the ending theme for the penultimate episode of the anime adaptation and as background music to one of the most awesome scenes in the true end of the visual novel.
There's also the main theme of the novel Gate of Steiner which manages to convey both a sinister conspiracy like tone and a sense of hope.
I Hope So, the opening theme from December When There Is No Angel sung by Ikeda Haruna.
Soul Requiem, from Lux Pain. It plays at the end of day twenty.
First Day, from High School Story, by Shigihara. It plays every time you level up, and it makes it feel even more satisfying.
While Hoshizora No Memoria has many, one that might come to mind for those that have played it would be the arranged version of the opening, "Eternal Recurrence". It is played in the most emotional scenes in the games, typically near the end of the various routes, be they heartwarming or tearjerking.