Add chord track (enable with LILYPOND_USE_CHORDS).

This is used for the drum guide track where too much detail would
distract from the click.

8 files changed, 77 insertions, 2 deletions

diff --git a/01-song1/01-song1.ly b/01-song1/01-song1.ly
index 6ace047..c115733 100644
--- a/01-song1/01-song1.ly
+++ b/01-song1/01-song1.ly
@@ -11,6 +11,7 @@
 \include "music/keys.ly"
 \include "music/stick.ly"
 \include "music/click.ly"
+\include "music/chords.ly"
 
 \layout {
   ragged-last = ##t
@@ -46,4 +47,8 @@ AllMusic = <<
   } { \stick }
 >>
 
+AllMusicMIDI = #(if (string-null? (getenv "LILYPOND_USE_CHORDS"))
+                 #{ \AllMusic #}
+                 #{ \chordTrack #})
+
 \include "../layouts.ly"
diff --git a/01-song1/music/chords.ly b/01-song1/music/chords.ly
new file mode 100644
index 0000000..7e5289a
--- /dev/null
+++ b/01-song1/music/chords.ly
@@ -0,0 +1,62 @@
+chordsA = \relative b {
+  \time 2/4
+  cis8 r cis r | r2 | r2 |
+  cis8 r cis r | r2 | \time 6/8 r2. |
+
+  \time 2/4
+  cis8 r cis r | r2 | r2   |
+  \time 4/4
+  \chordmode { cis4.:m c:m5- cis4:m ~ | q1 | }
+}
+
+chordsAextended = \chordmode {
+  cis4.:m fis:m5- cis4:m7 ~ | q1 |
+  cis4.:m c:m5- cis4:m ~ | q1 |
+  cis4.:m fis:m5- cis4:m7 ~ | q1 |
+}
+
+chordsVerse = \chordmode {
+  cis1:m ~    | q1 |
+  e2. b,4 ~   | q1 |
+  cis1:m ~    | q1 |
+  e2. b,4 ~   | q1 |
+  a,1:maj7 ~  | q1 |
+  a,2. b,4 ~  | q1 |
+}
+
+chordTrack = \relative b {
+  \set PianoStaff.midiInstrument = #"electric piano 1"
+  \chordmode {
+    %% intro
+    \repeat volta 4 {
+      \repeat volta 3 {
+        b,4 r8 cis2:m r8 |
+      }
+      e2 b,2
+    }
+  }
+
+  %% A
+  \repeat volta 2 \chordsA
+
+  \chordsAextended
+  \chordmode { e2. a4 ~ | a1 ~ | q1 | }
+
+  %% verses
+  \repeat volta 3 \chordsVerse
+  \transpose cis bes \chordsVerse
+  \chordsVerse
+
+  \repeat volta 2 \chordsA
+  \chordsAextended
+  \keysATransitionVariant
+
+  \nastyPause
+  \keysNasty
+  \keysWaltz
+  \repeat volta 2 \chordsA
+  \chordsAextended
+  \keysATransitionPreOutro
+  \repeat volta 2 \keysOutro
+  \keysEnd
+}
diff --git a/02-song2/02-song2.ly b/02-song2/02-song2.ly
index b90fb30..160aa2d 100644
--- a/02-song2/02-song2.ly
+++ b/02-song2/02-song2.ly
@@ -54,4 +54,6 @@ AllMusic = <<
   } { \tabChordRepeats \guitar }
 >>
 
+AllMusicMIDI = AllMusic
+
 \include "../layouts.ly"
diff --git a/03-circus/03-circus.ly b/03-circus/03-circus.ly
index 0f9d5de..9dc3e19 100644
--- a/03-circus/03-circus.ly
+++ b/03-circus/03-circus.ly
@@ -49,4 +49,6 @@ AllMusic = <<
   } { \stick }
 >>
 
+AllMusicMIDI = AllMusic
+
 \include "../layouts.ly"
diff --git a/04-white-noise/04-white-noise.ly b/04-white-noise/04-white-noise.ly
index 2073b1f..27aba8f 100644
--- a/04-white-noise/04-white-noise.ly
+++ b/04-white-noise/04-white-noise.ly
@@ -47,4 +47,6 @@ AllMusic = <<
   } { \stick }
 >>
 
+AllMusicMIDI = AllMusic
+
 \include "../layouts.ly"
diff --git a/Makefile b/Makefile
index 7d3199b..c9db328 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@ SOUNDFONT = $(HOME)/soundfonts/FluidR3GM.sf2
 # Determine how many processors are present
 CPU_CORES=`grep -m1 "cpu cores" /proc/cpuinfo | tr -cd '[:digit:]'`
 # The command to run lilypond
-LILY_CMD = lilypond -dinclude-settings=settings.ly -ddelete-intermediate-files -drelative-includes -djob-count=$(CPU_CORES)
+LILY_CMD = LILYPOND_USE_CHORDS=$(LILYPOND_USE_CHORDS) lilypond -dinclude-settings=settings.ly -ddelete-intermediate-files -drelative-includes -djob-count=$(CPU_CORES)
 
 SUBDIRS := 01-song1 02-song2 03-circus 04-white-noise
 
diff --git a/README.org b/README.org
index 5551ee2..8447221 100644
--- a/README.org
+++ b/README.org
@@ -23,3 +23,5 @@ To build a drum guide track with click:
 #+BEGIN_SRC sh
 make guide
 #+END_SRC
+
+When the environment variable =LILYPOND_USE_CHORDS= is set a simplified chord track is rendered for use as a drum guide.
diff --git a/layouts.ly b/layouts.ly
index b382da2..708d0e0 100644
--- a/layouts.ly
+++ b/layouts.ly
@@ -3,7 +3,7 @@
 \score {
   \unfoldRepeats {
     <<
-      \AllMusic
+      \AllMusicMIDI
       \new DrumStaff { \click }
     >>
   }