This is four clarinets playing one song. The first clarinet is the treble and the main melody. The second clarinet is the bass of the song to add more to the song. The third clarinet is a treble supporting the bass because it sounds nice. And finally, the fourth clarinet is some quarter notes of the bass and some quarter notes of the treble supporting the bass and I added this because you here it in the song it makes the song sound cooler.