Need help figuring out how to run a song uninterrupted

This is a War card game app that Rick Rolls you when you press deal. Everything works fine in the app. I just can't figure out how to keep the song from starting over every time the user presses the button.

@IBAction func dealTapped(_ sender: Any) {
    playBackGroundMusic(fileNamed: "Rick Astley - Never Gonna Shoot Your Stars.mp3")

    let leftNumber = Int.random(in: 2...14)
    let rightNumber = Int.random(in: 2...14)

    leftImageView.image = UIImage(named: "card\(leftNumber)")
    rightImageView.image = UIImage(named: "card\(rightNumber)")

    if leftNumber > rightNumber {
        leftScore += 1
        leftScoreLabel.text = String(leftScore)
    } else if leftNumber < rightNumber {
        rightScore += 1
        rightScoreLabel.text = String(rightScore)
    } else {

    }