Help with project - Arduino melody

We have project to create a melody using only the Arduino uno and buzzer. In addition the code must be in assembly. I managed to create a tone but I can't find a way to actually string tones to make melody

.device atmega168   ; mandatory stuff !
.equ DDRB =4 
.equ PORTB =5


again:

	ldi r16, $10 ; register 16 now contains 0001 0000
	ldi r17, $0 ; register 17 now contains 0000 0000

	out DDRB, r16 ; connect the buzz to a pin
	; ////////////////////////////////////////////////////// fisrt note
	out PORTB, r16 ; turn the led on
	ldi r18, 200
	ldi r19, 200


	first:
	dec r18
	brne first
	ldi r18, 20
	dec r19
	brne first
	 


	out PORTB, r17 ; turn the led off

	ldi r18,  200
	ldi r19,  200

	second:
	dec r18
	brne second
	ldi r18, 200
	dec r19
	brne second

Why don't you ask your teacher for advice?

In the real world we avoid using assembly unless there is really no other way to accomplish the task. In this case the tone library would be the obvious solution.

When posting code post all of it, what you posted will not produce a tone because there is no branch back to the again label.

Also you should follow the setup / loop structure by having stuff that should only be done once only done once.