Music is much more important than graphics when talking about immersion.
The Witcher 1 was way more immersive than The Witcher 2 specially because of the OST.
Every song must be unique and perfectly crafted in order to achieve the best possible experience. I hope The Witcher 3 OST is getting the attention it deserves.
We need a more nostalgic feeling...
It is the last part of the legend. Geralt's personal story must be fulfilled with great compositions so people can get vibes and emotions while playing through it.
I didn't hear anything related to the music in any of those E3 2014 interviews...
A great RPG needs a great soundtrack. That's what I call art for the senses.
Fortunately Konrad Tomaszkiewicz is aware of that. The immersion is directly related to music. I am sure The Witcher 3 will have a memorable OST. The few themes I've heard sound perfect. Not only the official ones like Hunt or be Hunted, The fields of Ard Skellige... but also these ones: