The music in the Elven Castle is calm and soothing.
The music in the Barbarian Castle is uplifting and boosts morale.)))
I don't like the music in Heroes of Might and Magic IV and V very much, and I don't remember the music in Heroes of Might and Magic II and I.
But mostly, I play with my own music, except for Heroes of Might and Magic V (it causes lag) =)))