diff --git a/chiptune_debug/Makefile b/chiptune_debug/Makefile
index f4a51d18..44193a42 100644
--- a/chiptune_debug/Makefile
+++ b/chiptune_debug/Makefile
@@ -5,10 +5,11 @@ PNG2GR = ../gr-utils/png2gr
 
 all:	chiptune_debug.dsk
 
-chiptune_debug.dsk:	CHIPTUNE_IRQ CHIPTUNE_NOIRQ ./sdemo.raw
+chiptune_debug.dsk:	CHIPTUNE_IRQ CHIPTUNE_NOIRQ CHIPTUNE_25HZ ./sdemo.raw
 	cp chiptune_empty.dsk chiptune_debug.dsk
 	$(DOS33) -y chiptune_debug.dsk BSAVE -a 0x0C00 CHIPTUNE_IRQ
 	$(DOS33) -y chiptune_debug.dsk BSAVE -a 0x0C00 CHIPTUNE_NOIRQ
+	$(DOS33) -y chiptune_debug.dsk BSAVE -a 0x0C00 CHIPTUNE_25HZ
 
 
 CHIPTUNE_IRQ:	chiptune_irq.o
@@ -29,8 +30,17 @@ chiptune_noirq.o:	chiptune_player.s \
 	zp.inc
 	ca65 -D NOIRQ=1 -o chiptune_noirq.o chiptune_player.s -l chiptune_noirq.lst
 
+CHIPTUNE_25HZ:	chiptune_25Hz.o
+	ld65 -o CHIPTUNE_25HZ chiptune_25Hz.o -C ../linker_scripts/apple2_c00.inc
+
+chiptune_25Hz.o:	chiptune_player.s \
+	mockingboard_a.s \
+	interrupt_handler.s \
+	zp.inc
+	ca65 -D F25HZ=1 -o chiptune_25Hz.o chiptune_player.s -l chiptune_25Hz.lst
+
 
 clean:
 	rm -f *~ TITLE.GR *.o *.lst \
-		CHIPTUNE_PLAYER CHIPTUNE_IRQ CHIPTUNE_NOIRQ
+		CHIPTUNE_PLAYER CHIPTUNE_IRQ CHIPTUNE_NOIRQ CHIPTUNE_25HZ
 
diff --git a/chiptune_debug/chiptune_debug.dsk b/chiptune_debug/chiptune_debug.dsk
new file mode 100644
index 00000000..b66e81c1
Binary files /dev/null and b/chiptune_debug/chiptune_debug.dsk differ
diff --git a/chiptune_debug/chiptune_player.s b/chiptune_debug/chiptune_player.s
index 61d6f90d..c826a773 100644
--- a/chiptune_debug/chiptune_player.s
+++ b/chiptune_debug/chiptune_player.s
@@ -52,14 +52,27 @@
 	sta	$C40D		; IFR: 1100, enable interrupt on timer one oflow
 	sta	$C40E		; IER: 1100, enable timer one interrupt
 
+.ifdef F25HZ
+        lda     #$40
+        sta     $C404           ; write into low-order latch
+        lda     #$9c
+        sta     $C405           ; write into high-order latch,
+                                ; load both values into counter
+                                ; clear interrupt and start counting
+
+        ; 9c40 / 1e6 = .040s, 25Hz
+
+
+.else
 	lda	#$E7
 	sta	$C404		; write into low-order latch
 	lda	#$4f
 	sta	$C405		; write into high-order latch,
 				; load both values into counter
 				; clear interrupt and start counting
-
 	; 4fe7 / 1e6 = .020s, 50Hz
+.endif
+
 .endif
 
 	;==================
diff --git a/linker_scripts/apple2_c00.inc b/linker_scripts/apple2_c00.inc
index 72588b0d..9704d857 100644
--- a/linker_scripts/apple2_c00.inc
+++ b/linker_scripts/apple2_c00.inc
@@ -4,7 +4,7 @@ MEMORY {
 }
 
 SEGMENTS {
-CODE: load = RAM, type = ro;
+CODE: load = RAM, type = ro, align = $100;
 RODATA: load = RAM, type = ro;
 DATA: load = RAM, type = rw;
 BSS: load = RAM, type = bss, define = yes;