The Music Modding System chooses a track to play by pulling info about the game's current situation and deciding from a list of cues that fit that situation in the music packs you have installed. For tactical tracks, the most basic situations are whether the player is currently in combat or in explore mode (no aliens on red alert,) but they can be made more specific by assigning specific environment and mission types that that cue will only play in.

The way I went about this was to give each track a generic cue (with no environment restrictions) and two more cues, each of which are restricted to a different environment. My intent was to make it so that, for example, the spooky tracks are twice as likely to play in the Abandoned and Slums environments, but I didn't want to restrict them to only play there, hence the generic cue that has a chance to play anywhere. (So anywhere that's not in those environments only has the chance to play the generic cue, but if MMS detects one of those environments, it has a chance to play either the generic cue or the cue tied only to that environment.)

If you've played FNF you know that when you retry a stage it plays a short sting, which I used as a sting in this pack for when every alien is killed. The old itch.io build had a pretty neat sting it used at the start screen so I decided to also add that as an alternate sting. To do this I added a duplicate for every combat cue that points to the itch.io sting, so you have a 50/50 chance of hearing a given track with the default Retry sting or the Start sting. So now, at worst you have twice the chance of hearing that track in any environment where it doesn't have a separate cue, and you're four times as likely to hear it in an environment where it does. Not terrible if you have a gazillion music packs like I do. (Yet.) Note that explore tracks aren't affected by this since they don't use stings, they still only have one generic cue and two different environment cues.

The Music Modding System has an option in the Mod Config Menu called "Mix Indifferent." Enabling this will make MMS ignore any additional restrictions beyond whether a cue is meant to play in combat or explore mode, so regardless of the environment it has a chance to choose any of each track's 6 cues (1 generic, 2 different environment restricted and then the duplicates with the alternate sting.) Coupled with the fact that most of these tracks have an instrumental variant included, you're essentially 12 times more likely to hear a song from this pack in combat, and 6 times more likely to hear it in explore mode. So if you're hearing tracks from this pack constantly, check first whether you have Mix Indifferent enabled.

1. Head to Steam > steamapps > workshop > content > 268500 (XCOM 2's folder)
   
   
2. Open folder 2471894842 (my mod's ID,) then the Config folder
   
   
3. The relevant files here are XComShellSound.ini, XComSkyrangerSound.ini, XComStrategySound.ini, and XComTacticalSound.ini (You can ignore the others)
   
   
4. For any entry you wish to disable, type ";" in front of each line to comment it out. If you wanted to disable Breakfast from playing at the main menu, its entry in XComShellSound.ini would look like ;+ShellCues="FNF_other.fnf.breakfast_Cue"

1. I only recommend doing this if you absolutely do not want to turn off "Mix Indifferent," or if you still think the tracks play too often without it.
   
   
2. Follow the steps above to find and open XComTacticalSound.ini
   
   
3. Because MMS needs every cue to have a unique ID, I differentiated them by referring to the default Retry sting with "VINNY" and the itch.io Start sting with "JOEL." Examples:
   
   +CombatDefs=(ID="FNFMusicPack_Combat_bopeebo_VINNY", \\
   XLoopCue="FNF_week1.fnf.bopeebo_Cue", \\
   XSting="FNF_stings.fnf.retry_Cue")
   
   +CombatDefs=(ID="FNFMusicPack_Combat_bopeebo_JOEL", \\
   XLoopCue="FNF_week1.fnf.bopeebo_Cue", \\
   XSting="FNF_stings.fnf.start_itch_shoot_Cue")
   
   
4. So, if you wanted to disable the itch.io Start variations of the tracks, Ctrl+F to find every track with "JOEL" in its ID and type ; at the start of each line to comment it out, or you can just delete them entirely. Same logic applies to the Retry variations, just search "VINNY" instead. Here's what it would look like commented out:
   
   +CombatDefs=(ID="FNFMusicPack_Combat_bopeebo_VINNY", \\
   XLoopCue="FNF_week1.fnf.bopeebo_Cue", \\
   XSting="FNF_stings.fnf.retry_Cue")
   
   ;+CombatDefs=(ID="FNFMusicPack_Combat_bopeebo_JOEL", \\
   ; XLoopCue="FNF_week1.fnf.bopeebo_Cue", \\
   ; XSting="FNF_stings.fnf.start_itch_shoot_Cue")
   
   
5. I labeled and organized every track in XComTacticalSound.ini by the week it appears in FNF to make it as easy and possible to go in and edit to your heart's content. Note that you won't have to do the VINNY / JOEL thing for Explore tracks since they don't use stings.
   
   
6. Remember to backup your edited XComTacticalSound.ini somewhere safe! I plan to eventually update this when the full game comes out, or as tracks are added to the free version.

If you have "Mix Indifferent" enabled in your MMS settings then every track in this pack is 6 times more likely to be played in combat, or 12 times if you count each track's instrumental variant! Turn it off, or if you're too attached to that setting see above for how to disable the extra cues manually.

Let me know of any other issues/questions you might have and I'll do my best to help.