在PHP中实现和理解适配器模式

Question

I am trying to learn the GoF design patterns. So far, I understand Singleton, Facade and Strategy. But I am stuck/confused with the adapter pattern. Here is how I tried to implement the pattern in PHP: [Summary: Rhythmbox is a music player, VLC is a video player. But I want to play music in VLC]

interface Listenable {
    public function playMusic();
}

interface Watchable {
    public function watchVideo();
}

class Music implements Listenable {
    public function playMusic() {
        echo 'Playing a music';   
    }
}

class Video implements Watchable {
    public function watchVideo() {
        echo 'Playing a video';   
    }
}

class Rhythmbox {
    public function play($music) {
        $music->playMusic();
    }
}

class VLC {
    public function watch($video) {
        $video->watchVideo();
    }
}

class VLCAdapter implements Watchable {
    public $music;

    public function __construct($music) {
        $this->music = $music;
    }
    public function watchVideo() {
        $this->music->playMusic();   
    }
}

(new VLCAdapter(new Music))->watchVideo(); # Why this?
(new Rhythmbox)->play(new Music); # Why not this?

But I think I didn't implement it properly. Either that or I am unable to comprehend it's significance. As I finished writing the adapter, something occurred to me: why would someone not use Rhythmbox directly to play the Music and use VLCAdapter instead?. At what point or under what circumstances should one opt for the VLCAdapter?

Can someone please explain how can one benefit from it? Or, what am I not understanding?