Combat music does not start in dialogue
Morrowind features numerous quests in which NPCs can become hostile to you in dialogue. All topics besides "Goodbye" will become greyed out, and in vanilla, this is when the exploration music ends and the combat music begins. In OpenMW the music will not transition until you have exited the dialogue window completely.
This does not apply to NPCs you've taunted into becoming hostile - in that case, the behavior is the same as in OpenMW. So it's not fully consistent in the vanilla game.
Tested with Foryn Gilnith in Seyda Neen (quest: "Death of a Taxman") and Fjol outside Hla Oad (quest: "Fjol the Outlaw")
#4 Updated by Andrei Kortunov about 2 months ago
taunt uses "Should Attack" editor function
Actally, successfull taunt just increases NPC Fight rating. The battle in this case starts after you close dialogue window.
With "StartCombat" battle starts immediately, but we update a music state in a different place.