Getting row identified by foreign key reference in laravel

I have a music streaming app. There are multiple songs in the app. Each user may "save" a song to their library.

So, the base model "song" has things like song_id,title,songduration,artist,album.

Then, there's a "usersong" model that has many rows. Each row is just a user_id and a song_id. When a user logs in, I get a list of songs they've saved by querying their user_id to that table. But, I'd like to get the full "song" row referenced by song_id, without having to store information in both songs and usersongs, and without having to make a 1000 individual queries.

Here is the "song" migration (shortened for simplicity):

  Schema::create('songs', function (Blueprint $table) {
        $table->string('id', 32);
        $table->string('title');
        $table->float('length');
})

Here is the "usersong" migration:

 Schema::create('usersongs', function (Blueprint $table) {
        $table->integer('user_id')->unsigned(); // a koel reference
        $table->string('song_id', 32);
        $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
        $table->foreign('song_id')->references('id')->on('songs')->onDelete('cascade'); 
        });

Here is the UserSong model, for the above schema. What's the best way to make the "getByUserId" function to return all "songs" belonging to the user with user_id, in a single query?

class UserSong extends Model
{

    protected $guarded = [];


    protected $table="usersongs";

    public function getByUserId($user_id){
        $this->where("user_id",$user_id)->get();
        /// how do I get the song rows automatically in this function?
    }
    protected $fillable=["user_id","song_id"];
}

Ideally I would call it in another script like:

$songs=UserSong::getByUserId($someuserid);

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