Why does calm4.ogg never play even if it is stored in the music folder?

In Minecraft, I am trying to get a removed track called Calm4 (calm4.ogg) to play in game since any music file under .minecraft/resources/music will play, and that is where I put the file. Because a track is randomly selected, I removed all other music in that folder and the newmusic folder just so that only Calm4 would play.

After loading a world, I am still hearing other tracks including those I have removed from the folders. Am I misunderstanding something, or will Calm4 never play in newer versions of the game?

The .minecraft/resources folder is not used, so any changes you make there will not affect the game. The folder you'll want is .minecraft/assets, but it will probably be easier to just create a resource pack.

For example, the following .minecraft/resourcepacks/NAME/assets/minecraft/sounds.json would add calm4 to the available music to be played.

{
    "music.game": {
        "category": "music",
        "sounds": [
            {
                "name": "music/game/calm4",
                "stream": true
            }
        ]
    }
}

You'd place calm4.ogg at .minecraft/resourcepacks/NAME/assets/minecraft/sounds/music/game/calm4.ogg within the same resource pack.

You'll still need a pack.meta file to define the pack, appearing at .minecraft/resourcepacks/NAME/pack.meta. Example content of that file:

{
    "pack": {
        "pack_format": 1,
        "description": "Adds calm4.ogg"
    }
}

You can find more information regarding sounds.json here.