The events that trigger different music cues isn't very well/at all explained anywhere. There's a small bit in Info.UTMusicManager that shows how it works in all gametypes except Warfare. Based off of the triggers from these gametypes an educated guess is all it takes to determine what causes additional changes in Warfare. Maybe someone other than myself may find this useful.
Intro
When - During pregame spec mode.
Note - If the intro is not set to loop it will play once and then change to Ambient.
Ambient
When - If no events are occurring (All flags are home, cores are safe, not in combat, match is over).
Note - This is a fallback cue to fade to after an event has passed.
Action
When - Whenever a player inflicts or receives damage.
Note -Action cues will override any other cue that may be playing and will continue to play until that event and the action event has passed. (ex: In CTF if you're supporting a FC and make it halfway home before taking fire the cue will change from Suspense to Action until you are dead or flag has been capped and action passed.)
Suspense
When - If someone else on your team takes a flag or when the enemy's core is vulnerable.
Note - If there are no players on the other team this will not play.
Tension
When - If enemy grabs your flag or if both teams have eachother's flag.
In Warfare plays if a teammate grabs an orb
If your team's orb has been dropped.
Victory
When - If you pickup a flag, orb, amp, or berserk.
Note - Possible juggernaut bug. Picking up one powerup will cue Victory. Picking up the second will cause Action to play for a second before switching back to Victory.
Intro
When - During pregame spec mode.
Note - If the intro is not set to loop it will play once and then change to Ambient.
Ambient
When - If no events are occurring (All flags are home, cores are safe, not in combat, match is over).
Note - This is a fallback cue to fade to after an event has passed.
Action
When - Whenever a player inflicts or receives damage.
Note -Action cues will override any other cue that may be playing and will continue to play until that event and the action event has passed. (ex: In CTF if you're supporting a FC and make it halfway home before taking fire the cue will change from Suspense to Action until you are dead or flag has been capped and action passed.)
Suspense
When - If someone else on your team takes a flag or when the enemy's core is vulnerable.
Note - If there are no players on the other team this will not play.
Tension
When - If enemy grabs your flag or if both teams have eachother's flag.
In Warfare plays if a teammate grabs an orb
If your team's orb has been dropped.
Victory
When - If you pickup a flag, orb, amp, or berserk.
Note - Possible juggernaut bug. Picking up one powerup will cue Victory. Picking up the second will cause Action to play for a second before switching back to Victory.
