I am not a pro at this kind of stuff but this is how I made looping sound in Snowblind:

radios()
{
    radiolist = getEntArray("radio_location", "targetname");
    for(i = 0; i < radiolist.size; i++)
    {
        radiolist[i] thread play_radio(radiolist[i]);
    }
}

play_radio(radio)
{
    rememberLastSong = -1;
    
    while(1)
    {
        wait randomIntRange(150,300);
        
        rand = randomInt(6);
        if(rand == rememberLastSong)
        rand = randomInt(6);

        rememberLastSong = rand;        
        radioSong = ("radio_song" + rand);
        
        radio playsound(radioSong);    
        wait 200;
    }
}

radios() //ADD THIS UNDER ZOMBIEMODE::MAIN IN mapname.gsc?
{
    radiolist = getEntArray("radio_location", "targetname");
    for(i = 0; i < radiolist.size; i++)
    {
        radiolist[i] thread play_radio(radiolist[i]);
    }
}

play_radio(radio) // and then paste this at the end of the .gsc?
{
    rememberLastSong = -1;
    
    while(1)
    {
        wait randomIntRange(150,300);
        
        rand = randomInt(6);
        if(rand == rememberLastSong)
        rand = randomInt(6);

        rememberLastSong = rand;        
        radioSong = ("radio_song" + rand);
        
        radio playsound(radioSong);    
        wait 200;
    }
}

//and then for the radiant part add a trigger with (targetname, radio_location) and then im done? is //that all?

oh sorry I will keep it simple:

radios()
{
    // For entities
    radiolist = getEntArray("radio_location", "targetname");
    
    // For structs, uncomment it if you use structs
    // radiolist = GetStructArray("radio_location", "targetname");
    
    for(i = 0; i < radiolist.size; i++)
    {
        radiolist[i] thread play_radio();
    }
}

play_radio(radio)
{
    while(1)
    {
        radio playsound("YOUR-SONG-NAME");
    
        // set here the time that you would like to wait.
        wait randomIntRange(150,300);
    }
    
    // you can also do this instead of using the whileloop
    // radio  playLoopSound ("YOUR-SONG-NAME");
}

You can add both of this at the bottom of your MAPNAME.gsc file
Then scroll up until you see this:

    /*--------------------
     ZOMBIE MODE
    ----------------------*/
    [[level.DLC3.weapons]]();
    [[level.DLC3.powerUps]]();    
    thread maps\dw_fx::init();    
    
    maps\_zombiemode::main();

under that add:

level thread radios();

Yes add entities or structs on the map and use the targetname: radio_location
 So it looks like this:

    /*--------------------
     ZOMBIE MODE
    ----------------------*/
    [[level.DLC3.weapons]]();
    [[level.DLC3.powerUps]]();    
    thread maps\dw_fx::init();    
    
    maps\_zombiemode::main();
    
    level thread radios();