Does the effect of the "magic" change based on someone's perception of the music? Everyone is effected by music in different ways - are they similarly affected by the "magic" in different ways?

For instance, I dislike ambiance because of the lack of tune. For a similar reason, I don't like most of Shostakovitch's works (and other composers with the same style) - it's too random and twangy and seems to lack melody altogether. I don't enjoy listening to music like that, and the only emotion I get out of it is chaos. However, if you like that style, you probably understand it better and can absorb the composer's intents better.

In the same way, people can also "zone out" sounds as they get used to them. Some people can completely ignore their surroundings and focus only on what they're doing. Can a "magic" lose effect if a person has become used to the sound? Can certain people ignore "magic" going on around them completely if their focus is elsewhere? And what of deaf people?

Or are you bypassing the act of hearing altogether? Does the music do its work, regardless of whether or not anyone is listening?

The idea of "words as music" struck out to me. There is a powerful world you can explore if you look into the effect of words. The Bible abounds with proverbs and instructions on the tongue, the fire which no man can tame, either working wonders or destroying lives. By translating that into "magic" and its more literal effects, you can teach or imply those morals with great power.

I like the idea of this premise. I love music, and I am aware of the effect sound can have. I think it would be interesting to see these effects represented more literally in a fantasy world. If most of the "magic" is fairly drastic (making very obvious and sudden changes in the surroundings), I agree that you will have to define what sounds truly produce an effect, lest things get chaotic and confusing. But on the flipside, I think it would also be interesting if all sound had a natural effect, however subtle. You could show, in a very beautiful way, how even the most mundane sounds bring depth to our world. Trees in the breeze, waves on the shore, someone's laugh. You wouldn't want, say, people turning into frogs (for an exaggerated example) every time someone laughed. But the sound, in a very small way, could bring color, lift spirits, lighten the air... And you could still show how music, if used expertly and purposefully, can wield a greater effect. Just a thought.

As a random idea, it would be interesting to follow (at least in part) a deaf person in this world. They'd have a curious take, and they already have a built-in struggle: they're despised. A deaf person would make a strong secondary character.

You know what would be quite fantastic and cruel? Make a character go deaf, whether suddenly or gradually, during the course of the book. Especially one that was (a) important to the MC and/or (b) had a "good life" ahead of him before the onset of deafness. Just a thought.

Wow. I'm so interested already that it almost isn't fair. So how would deaf people survive in a world like this? Would they be almost entirely helpless?