The 'Redemption Song' instrumental version is also great. The melody has a sense of hope and resilience which can mirror the different phases in a life story. It has a slow and steady tempo that gives a feeling of contemplation, much like reflecting on one's life.
One characteristic is the use of motifs. For example, in 'Peter and the Wolf' by Prokofiev, each character has a distinct musical motif. The flute represents the bird, and its light and fluttery melody tells the story of the bird's movements and actions. This helps the listener to follow the story easily.
Well, the anime adaptation of 'Angel Beats!' focuses more on the visual and auditory aspects to convey the story. However, the light novel has the advantage of being able to describe things in greater detail. For example, the descriptions of the afterlife environment in the light novel are more elaborate. In terms of the story, the light novel might have some extra sub - plots or character interactions that didn't make it into the anime. The light novel also gives the reader more freedom to imagine the scenes at their own pace.
One common element is a shared activity. For instance, if it's an art - related instrumental love story, painting together could be that element. Another could be a specific location. Just like in the example of the library before, a place can be a common element.
An 'instrumental love story' could be a love story where music or some other form of art or tool (instrument in a broad sense) plays a significant role. For example, two musicians might fall in love while playing music together, and the music they create becomes an integral part of their relationship.