SN76489: Do not play when period is overflowing

Source/Apps/Tune/Tune.asm

@@ -2002,7 +2002,7 @@ PLAYVIAHBIOS:
 	LD	C, 0
 	LD	HL, (AYREGS+TonA)
 	ld	a, h
-	AND	$3F
+	AND	$0F
 	LD	H, A
 	RST	08
 
@@ -2027,7 +2027,7 @@ PLAYVIAHBIOS:
 	LD	C, 0
 	LD	HL, (AYREGS+TonB)
 	ld	a, h
-	AND	$3F
+	AND	$0F
 	LD	H, A
 	RST	08
 
@@ -2052,7 +2052,7 @@ PLAYVIAHBIOS:
 	LD	C, 0
 	LD	HL, (AYREGS+TonC)
 	ld	a, h
-	AND	$3F
+	AND	$0F
 	LD	H, A
 	RST	08
 

Source/HBIOS/sn76489.asm

@@ -156,8 +156,12 @@ SN7_PITCH:
 	XOR	A			; SIGNAL SUCCESS
 	RET
 
-SN7_QUERY_PITCH1:
-	OR	$FF
+SN7_QUERY_PITCH1:			; REQUESTED PERIOD IS LARGER THAN THE SN76489 CAN SUPPORT
+	LD	L, $FF
+	LD	H, $FF
+	LD	(PENDING_PITCH), HL
+
+	OR	$FF			; SIGNAL FAILURE
 	RET
 
 SN7_PLAY:
@@ -165,12 +169,27 @@ SN7_PLAY:
 	AUDTRACE_D
 	AUDDEBUG("\r\n")
 
+	LD	A, (PENDING_PITCH + 1)
+	CP	$FF
+	JR	Z, SN7_PLAY1		; PERIOD IS TOO LARGE, UNABLE TO PLAY
 	CALL	SN7_APPLY_VOL
 	CALL	SN7_APPLY_PIT
 
 	XOR	A			; SIGNAL SUCCESS
 	RET
 
+SN7_PLAY1:				; TURN CHANNEL VOL TO OFF AND STOP PLAYING
+	LD	A, (PENDING_VOLUME)
+	PUSH	AF
+	LD	A, 0
+	LD	(PENDING_VOLUME), A
+	CALL	SN7_APPLY_VOL
+	POP	AF
+	LD	(PENDING_VOLUME), A
+
+	OR	$FF			; SIGNAL FAILURE
+	RET
+
 SN7_QUERY:
 	LD	A, E
 	CP	BF_SNDQ_CHCNT