Alien 8: Routine at B619

B619: The sound of a thud

Used by the routines at SCENE_TOOL, WANDERER and PACER. Four blips of three waves at pitches read from the start of the ROM, made low by setting their top two bits. Used as the creatures turn (WANDERER, PACER) and by SCENE_TOOL. As Knight Lore's sound_thud.
THUD_SOUND	B619	LD HL,$0000	four, from the ROM's first bytes
	B61C	LD E,$04	four, from the ROM's first bytes
THUD_SOUND_0	B61E	LD C,$03	three waves at the next ROM byte OR $C0
	B620	LD A,(HL)
	B621	INC HL
	B622	OR $C0
	B624	LD B,A
	B625	CALL BEEP
	B628	DEC E	until E runs out
	B629	JR NZ,THUD_SOUND_0
	B62B	RET