This is usually a missing requirement or something broke and mod didn't load.
Open the debug console (press ~) after starting a run and see if there are any error messages, if you see a message saying "SM ERROR: Repentogon or Music Mod Callback is required for Soundtrack Menu." then you just need to get either of those mods running first, both are linked in the description.

If the mod broke there will be an error message in the debug console that says what the bug is which file and which line of code, downloads can occasionally be a little messed up and files can sometimes be corrupted, while it's rare it has happened enough times to be something to check for, deleting the mod from your computer should cause steam to download a fresh copy, then restart the game and check again, if it still has an error post it here.


Make sure you don't have another mod on that controls music, when you change rooms soundtrack menu checks if the right music is playing, if not it starts the music it thinks should be playing, if another mod is controlling the music the music it plays may not match up with what the soundtrack menu is expecting, causing them to fight over it


There's something wrong with your music.xml setup and the track listing for the main menu doesn't exist, these listings are set by the music callback mod, not the soundtrack menu

So make sure that you have the correct version of the music callback mod (and also that you don't have both versions enabled at the same time, some people have done that)
alternatively your local version of the music callback mod might be corrupted, you can delete it or unsubscribe and then redownload it


Make sure the soundtrack you want selected is shown at the top of the menu screen and that you're not on "Custom" mode.
So many times someone has complained about this and it's ended up just being them setting the menu into custom mode and then setting the music for a floor they aren't on.

When setting music in custom mode the music will play temporarily just so you can know what song you're picking, that music will stop playing once you change rooms, leading to the "it just goes back to default" behaviour.

Another potential cause for this is having the add-on mod that gives each character their own soundtrack enabled, it overwrites the soundtrack menus selection, so if you have that on and change the soundtrack in the menu rather than in the settings for the add-on your change could just be immediately reverted.


While soundtrack menu tries to handle compatibility with custom floors it can still be weird depending on your specific setup and which mods are running, to accommodate different setups and preferences the soundtrack menu has an option with multiple different settings for how to handle stageAPI floors.

Open the soundtrack menu and scroll left, past the built-in soundtracks, past shuffle and custom modes, until you get to the options tab, then scroll down and you should see an option for stageAPI, change this setting, then return the soundtrack menu to your preferred soundtrack and play around for a bit, if it's still not quite right for you then try a different setting.


If one soundtrack mod has issues and fails to be loaded in properly it can mess with the loading system, causing the rest of the soundtracks that should be loaded after it to not be added to the menu, try disabling certain soundtrack mods you have and hopefully you find the culprit fairly quickly.

...I keep running into an issue where the Beast fight just... Won't play any music. It's been the same every time I've gotten to it, and I don't know what's causing it.
The only thing that's fixed it during the fight is exiting the run and turning it off, and that's just irritating. I even turned off Beast Tweaks, and that didn't work. Maybe it's my Ultra Conquest Mod causing it, but I haven't encountered him once, let alone while using Soundtrack Menu, so I don't know why that would break anything.

if you run the game with just music callback and mod menu and soundtrack menu mods enabled and no others, and use the console to skip to beast does it work then? just the quickest way to check if it is a mod compatibility problem

I just went to the beast recently while making updates to the DOOM soundtrack to check and music played there so if it's not a mod conflict then I'm not sure what would cause that, other than maybe having the AB+ version of music callback mod? having that enabled can mess with repentance tracks

with the greed in normal mod the "calm" replacement plays after defeating ultra greed in hard mode and continues into the ultra greedier fight. i asked the dev of the mod and they said it's an issue with soundtrack mod specifically that they're unable to fix.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3280852083

makes sense, MMC checks for being in a boss room and having no enemies active to play the calm music, and there's the gap between greed dying and greedier becoming active, it's also probably only checking for greed/greedier while in greed mode
shouldn't be too difficult to fix

cool. thanks!

I think one of the more recent updates messed with the music in CustomStageAPI floors (such as Boiler), as it plays whatever your Catacombs theme is set to. I only have one other mod affecting the music (that being a mod that replaces the default heart, Isaac, and Satan themes), so I have no clue what's causing it.

I've updated the mod so there's a setting in the menu for whether to play custom soundtracks while in a stageAPI floor or let the stageAPI floor music play regardless of chosen soundtrack.

The option wasn't always showing in the menu, and I accidentally left the override stageAPI setting as true by default rather than false, I have updated the mod to fix that, if the setting is still on for you it is in the "other" section under the menu music selection, left of "jingles only".

I can't see the option

"MC_POST_RENDER" from "Soundtrack Menu" failed: ...ng of Isaac Rebirth/mods/musicpicker_1933285222/main.lua:1308: attempt to index a nil value (field 'BossMusic')
Stack Traceback:
...ng of Isaac Rebirth/mods/musicpicker_1933285222/main.lua:1308: in function at line 1203

This error pops up when ever i fight mom, the boss intro music doesn't play and resorts to whatever floor i am currently in. (after the intro music the mom fight music plays as normal) also it seems that any mini boss encountered in depths II has the ambush music reverted back to the depths II music or whatever it is set too in custom mode. However repentagon does not give me an error for it.

its a part of a stageAPI custom floor check, getting the music set for the boss of the custom floor in the stageAPI settings, next update will include a check to see if there is no boss music set

this error also seems to pot up when starting Greed/Greedier mode! I have a similar error to the one above.

"MC_MAIN_MENU_RENDER" from "Soundtrack Menu" failed: ...ng of Isaac Rebirth/mods/musicpicker_1933285222/main.lua:2307: attempt to perform arithmetic on a nil value (upvalue 'chosenmainmenutrack')
Stack Traceback:
...ng of Isaac Rebirth/mods/musicpicker_1933285222/main.lua:2307: in function at line 2294

you already seem to be aware of the issue so i doubt this is new information. just thought I'd throw this here!
(additionally i'm having issues adjusting the settings for this in the mod config menu. maybe a similar bug?)

weird, the value it says is nil starts at 0 and is set to a number on game start, at first glance I would guess maybe the save file wasn't loaded correctly? and yeah if the value isn't a number the menu will probably have issues displaying and changing it, will fix

got this error when in the hot potato challenge on womb 1 where the stage music replaced the boss intro music which continued into the other floors of the challenge. i started a run on the pica run challenge and then r keyed only to have the music stop playing. entered a treasure room and exited and the music continued as normal.

"MC_POST_RENDER" from "Soundtrack Menu" failed: ...ng of Isaac Rebirth/mods/musicpicker_1933285222/main.lua:1308: attempt to index a nil value (field 'BossMusic')
Stack Traceback:
...ng of Isaac Rebirth/mods/musicpicker_1933285222/main.lua:1308: in function at line 1203

yeah, same issue as chowder, it's been fixed (just not uploaded yet, will be soon)