diff --git a/apps/led1/led1.c b/apps/led1/led1.c
index 7e32e1b..1381f94 100644
--- a/apps/led1/led1.c
+++ b/apps/led1/led1.c
@@ -33,7 +33,6 @@ int main (void)
         count++;
         if (count >= period)
             count = 0;
-
     }
 
     return 0;
diff --git a/apps/squeak0/Makefile b/apps/squeak0/Makefile
new file mode 100644
index 0000000..cc9aad6
--- /dev/null
+++ b/apps/squeak0/Makefile
@@ -0,0 +1,63 @@
+# File:   Makefile
+# Author: M. P. Hayes, UCECE
+# Date:   12 Sep 2010
+# Descr:  Makefile for squeak0
+
+# Definitions.
+CC = avr-gcc
+CFLAGS = -mmcu=atmega32u2 -Os -Wall -Wstrict-prototypes -Wextra -g -I../../drivers/avr -I../../extra -I../../drivers -I../../utils
+OBJCOPY = avr-objcopy
+SIZE = avr-size
+DEL = rm
+
+
+# Default target.
+all: squeak0.out
+
+
+# Compile: create object files from C source files.
+squeak0.o: squeak0.c ../../drivers/avr/pio.h ../../drivers/avr/system.h ../../drivers/avr/timer.h ../../extra/mmelody.h ../../extra/ticker.h ../../extra/tweeter.h ../../utils/task.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+pio.o: ../../drivers/avr/pio.c ../../drivers/avr/pio.h ../../drivers/avr/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+system.o: ../../drivers/avr/system.c ../../drivers/avr/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+timer.o: ../../drivers/avr/timer.c ../../drivers/avr/system.h ../../drivers/avr/timer.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+mmelody.o: ../../extra/mmelody.c ../../drivers/avr/system.h ../../extra/mmelody.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+ticker.o: ../../extra/ticker.c
+	$(CC) -c $(CFLAGS) $< -o $@
+
+tweeter.o: ../../extra/tweeter.c ../../drivers/avr/system.h ../../extra/ticker.h ../../extra/tweeter.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+task.o: ../../utils/task.c ../../drivers/avr/system.h ../../drivers/avr/timer.h ../../utils/task.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+
+
+# Link: create ELF output file from object files.
+squeak0.out: squeak0.o pio.o system.o timer.o mmelody.o ticker.o tweeter.o task.o
+	$(CC) $(CFLAGS) $^ -o $@ -lm
+	$(SIZE) $@
+
+
+# Target: clean project.
+.PHONY: clean
+clean: 
+	-$(DEL) *.o *.out *.hex
+
+
+# Target: program project.
+.PHONY: program
+program: squeak0.out
+	$(OBJCOPY) -O ihex squeak0.out squeak0.hex
+	dfu-programmer atmega32u2 erase; dfu-programmer atmega32u2 flash squeak0.hex; dfu-programmer atmega32u2 start
+
+
diff --git a/apps/squeak0/Makefile.test b/apps/squeak0/Makefile.test
new file mode 100644
index 0000000..d84d095
--- /dev/null
+++ b/apps/squeak0/Makefile.test
@@ -0,0 +1,61 @@
+# File:   Makefile
+# Author: M. P. Hayes, UCECE
+# Date:   11 Sep 2010
+# Descr:  Makefile for squeak1
+
+CC = gcc
+CFLAGS = -Wall -Wstrict-prototypes -Wextra -g -I../../drivers/test -I../../drivers -I../../extra -I../../utils
+
+DEL = rm
+
+
+# Default target.
+all: squeak1
+
+
+# Compile: create object files from C source files.
+squeak1-test.o: squeak1.c ../../drivers/led.h ../../drivers/test/avrtest.h ../../drivers/test/pio.h ../../drivers/test/system.h ../../drivers/test/timer.h ../../extra/mmelody.h ../../extra/ticker.h ../../extra/tweeter.h ../../utils/task.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+led-test.o: ../../drivers/led.c ../../drivers/led.h ../../drivers/test/avrtest.h ../../drivers/test/pio.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+mgetkey-test.o: ../../drivers/test/mgetkey.c ../../drivers/test/mgetkey.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+pio-test.o: ../../drivers/test/pio.c ../../drivers/test/avrtest.h ../../drivers/test/pio.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+system-test.o: ../../drivers/test/system.c ../../drivers/test/avrtest.h ../../drivers/test/mgetkey.h ../../drivers/test/pio.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+timer-test.o: ../../drivers/test/timer.c ../../drivers/test/system.h ../../drivers/test/timer.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+mmelody-test.o: ../../extra/mmelody.c ../../drivers/test/system.h ../../extra/mmelody.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+ticker-test.o: ../../extra/ticker.c
+	$(CC) -c $(CFLAGS) $< -o $@
+
+tweeter-test.o: ../../extra/tweeter.c ../../drivers/test/system.h ../../extra/ticker.h ../../extra/tweeter.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+task-test.o: ../../utils/task.c ../../drivers/test/system.h ../../drivers/test/timer.h ../../utils/task.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+
+
+
+# Link: create executable file from object files.
+squeak1: squeak1-test.o led-test.o mgetkey-test.o pio-test.o system-test.o timer-test.o mmelody-test.o ticker-test.o tweeter-test.o task-test.o
+	$(CC) $(CFLAGS) $^ -o $@ -lrt
+
+
+# Clean: delete derived files.
+.PHONY: clean
+clean: 
+	-$(DEL) squeak1 squeak1-test.o led-test.o mgetkey-test.o pio-test.o system-test.o timer-test.o mmelody-test.o ticker-test.o tweeter-test.o task-test.o
+
+
+
diff --git a/apps/squeak0/doc/Makefile b/apps/squeak0/doc/Makefile
new file mode 100644
index 0000000..080d1a7
--- /dev/null
+++ b/apps/squeak0/doc/Makefile
@@ -0,0 +1,42 @@
+# File:   Makefile
+# Author: M. P. Hayes, UCECE
+# Date:   11 Sep 2010
+# Descr:  Makefile for squeak0 docs
+
+DEL = rm
+
+all: file_dependencies.pdf module_dependencies.pdf makefile_dependencies.pdf build_dependencies.pdf callgraph.pdf
+
+file_dependencies.pdf: files.d 
+	../../../etc/graphdeps.py $< --out $@
+
+module_dependencies.pdf: modules.d 
+	../../../etc/graphdeps.py $< --modules --out $@
+
+makefile_dependencies.pdf: ../Makefile
+	../../../etc/graphdeps.py $< --out $@
+
+build_dependencies.pdf: ../Makefile
+	../../../etc/graphdeps.py $< --out $@ --showops
+
+callgraph.pdf: callgraph.d
+	../../../etc/graphdeps.py --calls --modules $< --out $@ --showops
+
+
+files.d: ../Makefile
+	(cd ..;	../../etc/makemake.py --relpath --files . . ../../drivers ../../drivers/avr ../../utils ../../extra --exclude system.h > doc/files.d)
+
+
+modules.d: ../Makefile
+	(cd ..;	../../etc/makemake.py --relpath --modules . . ../../drivers ../../drivers/avr ../../utils ../../extra --exclude system > doc/modules.d)
+
+
+callgraph.d: ../Makefile
+	(cd ..;	../../etc/makemake.py --cc="avr-gcc" --cflags="-Os -mmcu=atmega32u2" --relpath --calls . . ../../drivers ../../drivers/avr ../../utils ../../extra --exclude system.h > doc/callgraph.d)
+
+
+# Clean: delete derived files.
+.PHONY: clean
+clean: 
+	-$(DEL) *.d *.pdf
+
diff --git a/apps/squeak0/doc/README b/apps/squeak0/doc/README
new file mode 100644
index 0000000..39a9712
--- /dev/null
+++ b/apps/squeak0/doc/README
@@ -0,0 +1,16 @@
+Running make in this directory will generate a number of PDF graphs.
+In the callgraph, the arrows means "calls".  In the dependency graphs,
+the arrows means "requires" (or "depends upon").
+
+callgraph.pdf             This shows the callgraph, i.e., what functions each
+                          function in the program calls.
+module_dependencies.pdf   This shows the dependencies between the modules.
+file_dependencies.pdf     This shows the dependencies between the files.
+makefile_dependencies.pdf This shows the dependencies required by make when
+                          building the program.
+build_dependencies.pdf    This is like makefile_dependencies.pdf but shows
+                          the operations performed to generate the new file.
+
+callgraph.d               This shows the callgraph in text format.
+files.d                   This shows the file dependencies in text format.
+modules.d                 This shows the module dependencies in text format.
diff --git a/apps/squeak0/imperial_march.mmel b/apps/squeak0/imperial_march.mmel
new file mode 100644
index 0000000..6c4b789
--- /dev/null
+++ b/apps/squeak0/imperial_march.mmel
@@ -0,0 +1 @@
+"*8<G///>3<D#//A#G///>2 ///D+///D+///D+///D#+//A#F#///D#//A#G/// ///"
diff --git a/apps/squeak0/squeak0.c b/apps/squeak0/squeak0.c
new file mode 100644
index 0000000..4e22994
--- /dev/null
+++ b/apps/squeak0/squeak0.c
@@ -0,0 +1,89 @@
+/** @file   squeak0.c
+    @author M.P. Hayes
+    @date   16 Sep 2011
+*/
+
+#include "system.h"
+#include "pio.h"
+#include "task.h"
+#include "tweeter.h"
+#include "mmelody.h"
+
+
+/* Connect piezo tweeter to outermost pins of UCFK4 P1 connector.  */
+#define PIEZO_PIO PIO_DEFINE (PORT_D, 6)
+
+/* Define polling rates in Hz.  */
+#define TWEETER_TASK_RATE 20000
+
+#define TUNE_TASK_RATE 100
+
+#define TUNE_BPM_RATE 200
+
+
+static tweeter_t tweeter;
+static mmelody_t melody;
+static mmelody_obj_t melody_info;
+static tweeter_obj_t tweeter_info;
+
+
+static const char tune1[] =
+{
+#include "imperial_march.mmel"
+"          :"
+};
+
+
+static void tweeter_task_init (void)
+{
+    static tweeter_scale_t scale_table[] = TWEETER_SCALE_TABLE (TWEETER_TASK_RATE);
+
+    tweeter = tweeter_init (&tweeter_info, TWEETER_TASK_RATE, scale_table);
+
+    pio_config_set (PIEZO_PIO, PIO_OUTPUT_LOW);
+}
+
+
+static void tweeter_task (__unused__ void *data)
+{
+    pio_output_set (PIEZO_PIO, tweeter_update (tweeter));
+}
+
+
+static void tune_task_init (void)
+{
+    melody = mmelody_init (&melody_info, TUNE_TASK_RATE, 
+			   (mmelody_callback_t) tweeter_note_play, tweeter);
+
+    mmelody_speed_set (melody, TUNE_BPM_RATE);
+
+    mmelody_play (melody, tune1);
+}
+
+
+static void tune_task (__unused__ void *data)
+{
+    mmelody_update (melody);
+}
+
+
+int main (void)
+{
+    /* There are two tasks:
+         the tweeter task plays the notes
+         the tune tasks sequences the tune.
+    */
+    task_t tasks[] =
+    {
+        {.func = tweeter_task, .period = TASK_RATE / TWEETER_TASK_RATE},
+        {.func = tune_task, .period = TASK_RATE / TUNE_TASK_RATE},
+    };
+
+    system_init ();
+
+    tweeter_task_init ();
+    tune_task_init ();
+
+    task_schedule (tasks, ARRAY_SIZE (tasks));
+    return 0;
+}
diff --git a/apps/squeak1/imperial_march.mmel b/apps/squeak1/imperial_march.mmel
index 4493630..6c4b789 100644
--- a/apps/squeak1/imperial_march.mmel
+++ b/apps/squeak1/imperial_march.mmel
@@ -1 +1 @@
-"*16<G///>3<D#//A#G///>2 ///D+///D+///D+///D#+//A#F#///D#//A#G/// ///"
+"*8<G///>3<D#//A#G///>2 ///D+///D+///D+///D#+//A#F#///D#//A#G/// ///"