diff --git a/README.md b/README.md
index b6e3bd3..d6604d9 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@
 ```
 
 This demo includes:
+
 - "Gymnopedie No.1" (Erik Satie)
 - "12 Variationen über ein französisches Lied 'Ah, vous dirai-je, maman'" (Wolfgang Amadeus Mozart)
 
@@ -31,8 +32,8 @@ or
 [mjapa.jp](https://music-school.mjapa.jp/) style (Both are quite similar).
 
 - Reference:
-    - [Mabinogi MML](https://wikiwiki.jp/mabinogi/%E9%9F%B3%E6%A5%BD/MML)
-    - [mjapa.jp MML](https://music-school.mjapa.jp/mml_to_midi_converter.html#mml_image)
+  - [Mabinogi MML](https://wikiwiki.jp/mabinogi/%E9%9F%B3%E6%A5%BD/MML)
+  - [mjapa.jp MML](https://music-school.mjapa.jp/mml_to_midi_converter.html#mml_image)
 
 Now basic manual is available: [MML Style Overview](./mml/AboutMMLStyle.md)
 
@@ -46,13 +47,42 @@ If you get ready:
 
 It converts MML to C array format.
 
-Copy the output, paste the array definitions beginning with `const` to above `songs` array in the file `src/songdata.c`,
-and paste the line of `{xxx_1, xxx_2, xxx_3, xxx_4},` into `songs`.
+(TODO: automate procedures from here.)
+
+Copy the output, paste the array definitions beginning with `const` to the separate file in the `src/` (e.g. `song_newsong.c`).
+
+Add the declaration of tracks of your song to the file (e.g. `const unsigned char *tracks_newsong[4] ={xxx_1, xxx_2, xxx_3, xxx_4}`).
 `xxx` is your song name.
 
+Create a new header (e.g. `src/song_newsong.h`) with contents similar to the following:
+
+```c
+extern const unsigned char *tracks_gymno1[4];
+```
+
+(TODO: automate procedures until here.)
+
+Modify `songdata.c` to include the header file, and add the track to `songs` array, like:
+
+```c
+#include "song_newsong.h"
+
+const uint8 **songs[] = {
+    tracks_gymno1, tracks_ttls, tracks_newsong
+    0 // sentinel
+};
+```
+
+Then add the object file requisites to `OSONGS` in `Makefile`. It will look like this:
+
+    OSONGS = \
+        song_ttls.o \
+        song_gymno1.o \
+        song_newsong.o
+
 Finally, run `make` in `src` directory, and play the ROM.
 
-Song index is your song's index in `songs` array.
+The songs are indexed in the order of `songs` array.
 
 ### About `mml2dmg`
 
diff --git a/TODO.md b/TODO.md
index 6744939..6414acb 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,5 +1,7 @@
 # TODO
 
-##### (1,2,3) is priority. 1 is the highest.
+The priority is shown in parentheses. 1 is the highest.
 
-    (1) 2021-09-14 Want to add the changeability of the envelope steps
+- [ ] (2) 2021-09-14 Want to add the changeability of the envelope steps
+- [ ] (2) 2024-01-01 Make MML converter with flex/bison for completeness
+- [ ] (2) 2024-01-01 Use `getopt` to parse options correctly
diff --git a/src/Makefile b/src/Makefile
index e1ce510..566b735 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,27 +1,35 @@
-AS = arm-none-eabi-as
-CC = arm-none-eabi-gcc
-LIBGCC = `arm-none-eabi-gcc -print-libgcc-file-name`
-CFLAGS = -Wall -O -fno-builtin -fomit-frame-pointer -finhibit-size-directive \
--fno-ident
+# include songs/songs.mk
+
+## Set this value correctly if the compiler tools are NOT in your PATH
+BINDIR = /opt/devkitpro/devkitARM/bin/
+
+AS = $(BINDIR)arm-none-eabi-as
+CC = $(BINDIR)arm-none-eabi-gcc
+LD = $(BINDIR)arm-none-eabi-ld
+OBJCOPY = $(BINDIR)arm-none-eabi-objcopy
+LIBGCC = `$(CC) -print-libgcc-file-name`
+CFLAGS = -Wall -O -fno-builtin -fomit-frame-pointer -finhibit-size-directive -fno-ident
 
 OUTNAME = main
-FILES = \
-	crt.o ${OUTNAME}.o \
+
+OSONGS = \
+	song_ttls.o \
+	song_gymno1.o
+
+OFILES = \
+	crt.o $(OUTNAME).o \
 	sounddrv.o songdata.o \
 	char_gfx/misaki_gothic_2nd_nega.o \
 	char_gfx/misaki_gothic_2nd.o \
-	bgobjmgr.o keyinput.o
-
+	bgobjmgr.o keyinput.o \
+	$(OSONGS)
 
-${OUTNAME}.bin: ${FILES} *.h
-	arm-none-eabi-ld -o ${OUTNAME}.out -T gcc.ls \
-	${FILES} ${LIBGCC}
-	arm-none-eabi-objcopy -O binary ${OUTNAME}.out ${OUTNAME}.bin
 
-all:	clean ${OUTNAME}.bin
+.PHONY: all clean
 
-emu:	${OUTNAME}.bin
-	mv ${OUTNAME}.bin ${OUTNAME}.gba && mgba-qt ${OUTNAME}.gba
+$(OUTNAME).gba: $(OFILES) *.h
+	$(LD) -o $(OUTNAME).out -T gcc.ls $(OFILES) $(LIBGCC)
+	$(OBJCOPY) -O binary $(OUTNAME).out $(OUTNAME).gba
 
 clean:
-	rm -f *.o *.out *.sav *.gba
+	-rm -f *.o *.out *.sav *.gba
diff --git a/src/exgba.h b/src/exgba.h
index d3140e9..e103beb 100644
--- a/src/exgba.h
+++ b/src/exgba.h
@@ -9,9 +9,9 @@
 
 /// Type definitions
 
-typedef unsigned char   byte;
-typedef unsigned short  hword;
-typedef unsigned int    word;
+typedef unsigned char   byte, uint8;
+typedef unsigned short  hword, uint16;
+typedef unsigned int    word, uint32;
 
 /// Register access
 
diff --git a/src/song_gymno1.c b/src/song_gymno1.c
new file mode 100644
index 0000000..46e5b03
--- /dev/null
+++ b/src/song_gymno1.c
@@ -0,0 +1,36 @@
+#include "meta.h"
+
+// GymnopedieNo1.mml, ID = GymnopedieNo1_mml
+static const unsigned char GymnopedieNo1_mml_1[] = {
+    134, 60,  129, 2,   138, 1,   132, 128, 133, 4,   129, 4,   138, 0,   128,
+    78,  81,  79,  78,  73,  71,  73,  74,  130, 2,   131, 1,   69,  130, 1,
+    131, 1,   66,  130, 1,   131, 1,   128, 128, 78,  81,  79,  78,  73,  71,
+    73,  74,  130, 2,   131, 1,   69,  129, 2,   138, 1,   73,  78,  130, 1,
+    131, 1,   64,  128, 129, 4,   138, 0,   69,  71,  72,  76,  74,  71,  74,
+    72,  71,  130, 1,   74,  128, 74,  76,  77,  79,  81,  72,  74,  76,  74,
+    71,  130, 1,   74,  128, 74,  130, 2,   131, 1,   79,  130, 2,   131, 1,
+    78,  71,  69,  71,  73,  74,  76,  73,  74,  76,  66,  62,  67,  130, 2,
+    131, 1,   72,  130, 2,   131, 1,   74,  TERM};
+static const unsigned char GymnopedieNo1_mml_2[] = {
+    132, 128, 130, 8,   59,  130, 8,   62,  66,  128, 130, 8,   57,  130, 8,
+    61,  66,  133, 8,   128, 130, 8,   57,  130, 8,   61,  66,  128, 130, 8,
+    59,  130, 8,   62,  66,  128, 55,  59,  128, 130, 8,   59,  130, 8,   62,
+    67,  128, 130, 8,   53,  130, 8,   57,  62,  128, 130, 8,   57,  130, 8,
+    60,  64,  128, 130, 8,   55,  130, 8,   59,  64,  129, 8,   130, 4,   128,
+    50,  55,  59,  64,  130, 4,   128, 48,  52,  57,  62,  130, 4,   128, 48,
+    54,  57,  62,  130, 4,   128, 57,  60,  130, 4,   65,  130, 4,   128, 57,
+    60,  130, 4,   64,  130, 4,   128, 50,  55,  59,  64,  130, 4,   128, 48,
+    52,  57,  62,  130, 4,   128, 48,  54,  57,  62,  130, 4,   128, 59,  64,
+    130, 4,   67,  130, 4,   128, 57,  61,  130, 4,   66,  130, 4,   128, 59,
+    62,  130, 4,   66,  130, 4,   128, 61,  64,  130, 4,   69,  130, 4,   128,
+    57,  61,  66,  69,  130, 4,   128, 130, 4,   57,  130, 4,   57,  130, 2,
+    131, 1,   60,  130, 2,   131, 1,   62,  TERM};
+static const unsigned char GymnopedieNo1_mml_3[] = {
+    129, 2,  138, 1,   132, 43,  38,  133, 8,  42, 47, 40,
+    40,  38, 45,  132, 38,  133, 9,   40,  42, 47, 40, 40,
+    130, 4,  40,  130, 4,   47,  130, 4,   52, 45, 38, TERM};
+static const unsigned char GymnopedieNo1_mml_4[] = {TERM};
+
+const unsigned char *tracks_gymno1[4] = {
+    GymnopedieNo1_mml_1, GymnopedieNo1_mml_2, GymnopedieNo1_mml_3,
+    GymnopedieNo1_mml_4};
diff --git a/src/song_gymno1.h b/src/song_gymno1.h
new file mode 100644
index 0000000..5208d78
--- /dev/null
+++ b/src/song_gymno1.h
@@ -0,0 +1 @@
+extern const unsigned char *tracks_gymno1[4];
diff --git a/src/song_ttls.c b/src/song_ttls.c
new file mode 100644
index 0000000..09be807
--- /dev/null
+++ b/src/song_ttls.c
@@ -0,0 +1,35 @@
+static const unsigned char Tinkle2LittleStar_cpped_1[] = {
+    60,  60,  67, 67,  69, 69, 67, 128, 65,  65,  64,  64, 62,  62, 60,  128,
+    67,  67,  65, 65,  64, 64, 62, 128, 67,  67,  65,  65, 64,  64, 62,  128,
+    60,  60,  67, 67,  69, 69, 67, 128, 65,  65,  64,  64, 62,  62, 60,  128,
+    132, 129, 16, 62,  60, 59, 60, 59,  60,  59,  60,  69, 67,  66, 67,  66,
+    67,  66,  67, 68,  69, 72, 71, 74,  72,  71,  69,  69, 67,  76, 74,  72,
+    71,  69,  67, 67,  65, 74, 72, 71,  69,  67,  65,  65, 64,  72, 71,  69,
+    67,  65,  64, 129, 8,  62, 69, 67,  59,  130, 2,   60, 133, 2,  129, 16,
+    69,  67,  66, 67,  66, 67, 69, 67,  67,  65,  64,  65, 64,  65, 67,  65,
+    65,  64,  63, 64,  63, 64, 65, 64,  64,  62,  61,  62, 61,  62, 64,  62,
+    69,  67,  66, 67,  76, 72, 69, 67,  67,  65,  64,  65, 74,  71, 67,  65,
+    65,  64,  63, 64,  72, 67, 65, 64,  130, 8,   131, 1,  67,  64, 130, 4,
+    62,  129, 16, 62,  60, 59, 60, 59,  60,  59,  60,  69, 67,  66, 67,  66,
+    67,  66,  67, 68,  69, 72, 71, 74,  72,  71,  69,  69, 67,  76, 74,  72,
+    71,  69,  67, 67,  65, 74, 72, 71,  69,  67,  65,  65, 64,  72, 71,  69,
+    67,  65,  64, 129, 8,  62, 69, 67,  59,  130, 2,   60, 255,
+};
+static const unsigned char Tinkle2LittleStar_cpped_2[] = {
+    36, 48, 52, 48, 53, 48, 52, 48, 50, 47, 48, 45, 41, 43,  36,  128, 52,
+    43, 50, 43, 48, 43, 47, 43, 52, 43, 50, 43, 48, 48, 43,  128, 36,  48,
+    52, 48, 53, 48, 52, 48, 50, 47, 48, 45, 41, 43, 36, 128, 132, 36,  48,
+    52, 48, 53, 48, 52, 48, 50, 47, 48, 45, 41, 43, 36, 128, 133, 2,   52,
+    43, 50, 43, 48, 43, 47, 43, 52, 43, 50, 43, 48, 48, 43,  128, 36,  48,
+    52, 48, 53, 48, 52, 48, 50, 47, 48, 45, 41, 43, 36, 128, 255,
+};
+static const unsigned char Tinkle2LittleStar_cpped_3[] = {
+    255,
+};
+static const unsigned char Tinkle2LittleStar_cpped_4[] = {
+    255,
+};
+
+const unsigned char *tracks_ttls[4] = {
+    Tinkle2LittleStar_cpped_1, Tinkle2LittleStar_cpped_2,
+    Tinkle2LittleStar_cpped_3, Tinkle2LittleStar_cpped_4};
diff --git a/src/song_ttls.h b/src/song_ttls.h
new file mode 100644
index 0000000..a7ab0fd
--- /dev/null
+++ b/src/song_ttls.h
@@ -0,0 +1 @@
+extern const unsigned char *tracks_ttls[4];
diff --git a/src/songdata.c b/src/songdata.c
index 05d89e2..0d88e54 100644
--- a/src/songdata.c
+++ b/src/songdata.c
@@ -1,23 +1,10 @@
 #include "meta.h"
+#include "song_ttls.h"
+#include "song_gymno1.h"
 
-// Tinkle2LittleStar.cpped, ID = Tinkle2LittleStar_cpped
-const unsigned char Tinkle2LittleStar_cpped_1[] = {60, 60, 67, 67, 69, 69, 67, 128, 65, 65, 64, 64, 62, 62, 60, 128, 67, 67, 65, 65, 64, 64, 62, 128, 67, 67, 65, 65, 64, 64, 62, 128, 60, 60, 67, 67, 69, 69, 67, 128, 65, 65, 64, 64, 62, 62, 60, 128, 132, 129, 16, 62, 60, 59, 60, 59, 60, 59, 60, 69, 67, 66, 67, 66, 67, 66, 67, 68, 69, 72, 71, 74, 72, 71, 69, 69, 67, 76, 74, 72, 71, 69, 67, 67, 65, 74, 72, 71, 69, 67, 65, 65, 64, 72, 71, 69, 67, 65, 64, 129, 8, 62, 69, 67, 59, 130, 2, 60, 133, 2, 129, 16, 69, 67, 66, 67, 66, 67, 69, 67, 67, 65, 64, 65, 64, 65, 67, 65, 65, 64, 63, 64, 63, 64, 65, 64, 64, 62, 61, 62, 61, 62, 64, 62, 69, 67, 66, 67, 76, 72, 69, 67, 67, 65, 64, 65, 74, 71, 67, 65, 65, 64, 63, 64, 72, 67, 65, 64, 130, 8, 131, 1, 67, 64, 130, 4, 62, 129, 16, 62, 60, 59, 60, 59, 60, 59, 60, 69, 67, 66, 67, 66, 67, 66, 67, 68, 69, 72, 71, 74, 72, 71, 69, 69, 67, 76, 74, 72, 71, 69, 67, 67, 65, 74, 72, 71, 69, 67, 65, 65, 64, 72, 71, 69, 67, 65, 64, 129, 8, 62, 69, 67, 59, 130, 2, 60, 255, };
-const unsigned char Tinkle2LittleStar_cpped_2[] = {36, 48, 52, 48, 53, 48, 52, 48, 50, 47, 48, 45, 41, 43, 36, 128, 52, 43, 50, 43, 48, 43, 47, 43, 52, 43, 50, 43, 48, 48, 43, 128, 36, 48, 52, 48, 53, 48, 52, 48, 50, 47, 48, 45, 41, 43, 36, 128, 132, 36, 48, 52, 48, 53, 48, 52, 48, 50, 47, 48, 45, 41, 43, 36, 128, 133, 2, 52, 43, 50, 43, 48, 43, 47, 43, 52, 43, 50, 43, 48, 48, 43, 128, 36, 48, 52, 48, 53, 48, 52, 48, 50, 47, 48, 45, 41, 43, 36, 128, 255, };
-const unsigned char Tinkle2LittleStar_cpped_3[] = {255, };
-const unsigned char Tinkle2LittleStar_cpped_4[] = {255, };
-
-// GymnopedieNo1.mml, ID = GymnopedieNo1_mml
-const unsigned char GymnopedieNo1_mml_1[] = {134, 60, 129, 2, 138, 1, 132, 128, 133, 4, 129, 4, 138, 0, 128, 78, 81, 79, 78, 73, 71, 73, 74, 130, 2, 131, 1, 69, 130, 1, 131, 1, 66, 130, 1, 131, 1, 128, 128, 78, 81, 79, 78, 73, 71, 73, 74, 130, 2, 131, 1, 69, 129, 2, 138, 1, 73, 78, 130, 1, 131, 1, 64, 128, 129, 4, 138, 0, 69, 71, 72, 76, 74, 71, 74, 72, 71, 130, 1, 74, 128, 74, 76, 77, 79, 81, 72, 74, 76, 74, 71, 130, 1, 74, 128, 74, 130, 2, 131, 1, 79, 130, 2, 131, 1, 78, 71, 69, 71, 73, 74, 76, 73, 74, 76, 66, 62, 67, 130, 2, 131, 1, 72, 130, 2, 131, 1, 74, TERM};
-const unsigned char GymnopedieNo1_mml_2[] = {132, 128, 130, 8, 59, 130, 8, 62, 66, 128, 130, 8, 57, 130, 8, 61, 66, 133, 8, 128, 130, 8, 57, 130, 8, 61, 66, 128, 130, 8, 59, 130, 8, 62, 66, 128, 55, 59, 128, 130, 8, 59, 130, 8, 62, 67, 128, 130, 8, 53, 130, 8, 57, 62, 128, 130, 8, 57, 130, 8, 60, 64, 128, 130, 8, 55, 130, 8, 59, 64, 129, 8, 130, 4, 128, 50, 55, 59, 64, 130, 4, 128, 48, 52, 57, 62, 130, 4, 128, 48, 54, 57, 62, 130, 4, 128, 57, 60, 130, 4, 65, 130, 4, 128, 57, 60, 130, 4, 64, 130, 4, 128, 50, 55, 59, 64, 130, 4, 128, 48, 52, 57, 62, 130, 4, 128, 48, 54, 57, 62, 130, 4, 128, 59, 64, 130, 4, 67, 130, 4, 128, 57, 61, 130, 4, 66, 130, 4, 128, 59, 62, 130, 4, 66, 130, 4, 128, 61, 64, 130, 4, 69, 130, 4, 128, 57, 61, 66, 69, 130, 4, 128, 130, 4, 57, 130, 4, 57, 130, 2, 131, 1, 60, 130, 2, 131, 1, 62, TERM};
-const unsigned char GymnopedieNo1_mml_3[] = {129, 2, 138, 1, 132, 43, 38, 133, 8, 42, 47, 40, 40, 38, 45, 132, 38, 133, 9, 40, 42, 47, 40, 40, 130, 4, 40, 130, 4, 47, 130, 4, 52, 45, 38, TERM};
-const unsigned char GymnopedieNo1_mml_4[] = {TERM};
-
-const unsigned char *songs[][MAX_CHAN] = {
-    {GymnopedieNo1_mml_1, GymnopedieNo1_mml_2, GymnopedieNo1_mml_3, GymnopedieNo1_mml_4},
-    {Tinkle2LittleStar_cpped_1, Tinkle2LittleStar_cpped_2, Tinkle2LittleStar_cpped_3, Tinkle2LittleStar_cpped_4},
-    0   // sentinel
+const uint8 **songs[] = {
+    tracks_gymno1, tracks_ttls,
+    0 // sentinel
 };
 
-const unsigned char *GetSongData(int index, int ch) {
-    return songs[index][ch];
-}
+const unsigned char *GetSongData(int index, int ch) { return songs[index][ch]; }