on_declared_war_play_music

on_declared_war_play_music = {
	###############################
	##### Attacker music
	###############################
	if = {
		limit = {
			exists = scope:war # silence error when building description before war exists
			scope:war = { using_holy_war_cb_trigger = yes } # going CB->war->is this war's CB a certain type->yes
		}
		scope:attacker = { play_music_cue = mx_cue_crusade_starts }
	}
	else_if = {
		limit = {
			exists = scope:war
			has_mpo_dlc_trigger = yes
			OR = {
				scope:attacker = {
					government_has_flag = government_is_nomadic
			  		any_character_situation = {
			  			this = situation:the_great_steppe
			  		}
				}
				scope:defender = {
					government_has_flag = government_is_nomadic
			  		any_character_situation = {
			  			this = situation:the_great_steppe
			  		}
				}
			}
		}
		scope:attacker = { play_music_cue = mx_cue_the_khans_glory }
	}
	else_if = {
		limit = {
			exists = scope:war
			OR = {
				scope:attacker = { fp3_character_any_involvement_persian_struggle_trigger = yes }
				scope:defender = { fp3_character_any_involvement_persian_struggle_trigger = yes }
			}
		}
		scope:attacker = { play_music_cue = strugglewar_cue }
	}
	else_if = {
		limit = {
			exists = scope:war
			OR = {
				scope:attacker = { fp2_character_any_involvement_iberian_struggle_trigger = yes }
				scope:defender = { fp2_character_any_involvement_iberian_struggle_trigger = yes }
			}
		}
		scope:attacker = { play_music_cue = mx_IberiaWar }
	}
	else_if = {
		limit = {
			exists = scope:war
			scope:attacker = { fp1_is_norse_tribal = yes }
		}
		scope:attacker = { play_music_cue = mx_raid }
	}
	else = {
		scope:attacker = { play_music_cue = mx_cue_war_declared }
	}
	###############################
	##### Defender music
	###############################
	if = {
		limit = {
			exists = scope:war
			OR = {
				scope:attacker = { fp2_character_any_involvement_iberian_struggle_trigger = yes }
				scope:defender = { fp2_character_any_involvement_iberian_struggle_trigger = yes }
			}
		}
		scope:defender = { play_music_cue = mx_IberiaWar }
	}
	else_if = {
		limit = {
			exists = scope:war
			has_mpo_dlc_trigger = yes
			OR = {
				scope:attacker = {
					government_has_flag = government_is_nomadic
			  		any_character_situation = {
			  			this = situation:the_great_steppe
			  		}
				}
				scope:defender = {
					government_has_flag = government_is_nomadic
			  		any_character_situation = {
			  			this = situation:the_great_steppe
			  		}
				}
			}
		}
		scope:defender = { play_music_cue = mx_cue_the_khans_glory }
	}
	else_if = {
		limit = {
			exists = scope:war
			OR = {
				scope:attacker = { fp3_character_any_involvement_persian_struggle_trigger = yes }
				scope:defender = { fp3_character_any_involvement_persian_struggle_trigger = yes }
			}
		}
		scope:defender = { play_music_cue = strugglewar_cue }
	}
	else_if = {
		limit = {
			exists = scope:war
			scope:attacker = { fp1_is_norse_tribal = yes }
		}
		scope:defender = { play_music_cue = mx_raid }
	}

	else = {
		scope:defender = {
			play_music_cue = mx_cue_war_declared
		}
	}
}

As written in game/common/scripted_effects/00_war_effects.txt.