Heartsinging
The idea that each person hears only what they need, as one aspect of the song the Heartsinger offers, is based on my understanding of sensory perception. Our eyes may all see the same image, but our perceptions will all be different. If we had the ability to share memories, I think we would be astounded to see the differences between a single shared experience and how it was remembered by two friends, much less two strangers. Is music any different? I believe it is fundamentally more complex and taps into our own set of experiences, giving us a broader range of interpretation. That is why a Heartsinger offers their song and each person takes away what they can from it. The same is true with any music produced, which is why one type of music is noise to some people and deeply meaningful to others.