From 617d9d75379510103b6a5ffa43e33c6936493e22 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Sat, 12 Mar 2011 21:01:42 +0100
Subject: [PATCH] Midi: allow alternate channel mappings: per instrument,
 staff, voice.

The property midiChannelMapping specifies the mapping of MIDI channels:
per instrument (default), staff or voice.

The default mapping, per instrument, makes for optimal re-using of
channels.  Per voice mapping allows re-creating of voices and
arranging them on staffs with the current midi2ly.  Per staff mapping
closely matches the old default.
---
 lily/staff-performer.cc           | 20 +++++++++++++++-----
 ly/performer-init.ly              |  1 +
 scm/define-context-properties.scm |  3 +--
 scripts/midi2ly.py                |  6 +++++-
 4 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/lily/staff-performer.cc b/lily/staff-performer.cc
index 5e124c8baf..3fc26fa456 100644
--- a/lily/staff-performer.cc
+++ b/lily/staff-performer.cc
@@ -117,6 +117,11 @@ Staff_performer::new_audio_staff (string voice)
 Audio_staff*
 Staff_performer::get_audio_staff (string voice)
 {
+  SCM channel_mapping = get_property ("midiChannelMapping");
+  if (channel_mapping == ly_symbol2scm ("voice")
+      && staff_map_.size ())
+    return staff_map_.begin ()->second;
+
   map<string, Audio_staff*>::const_iterator i = staff_map_.find (voice);
   if (i != staff_map_.end ())
     return i->second;
@@ -201,8 +206,9 @@ Staff_performer::new_instrument_string ()
 int
 Staff_performer::get_channel (string instrument)
 {
-  SCM channel_per_staff = get_property ("midiChannelPerStaff");
-  map<string, int>& channel_map = (channel_per_staff == SCM_BOOL_T)
+  SCM channel_mapping = get_property ("midiChannelMapping");
+  map<string, int>& channel_map
+    = (channel_mapping != ly_symbol2scm ("instrument"))
     ? channel_map_
     : static_channel_map_;
 
@@ -210,9 +216,9 @@ Staff_performer::get_channel (string instrument)
   if (i != channel_map.end ())
     return i->second;
  
-  int channel = (channel_per_staff == SCM_BOOL_T)
+  int channel = (channel_mapping == ly_symbol2scm ("staff"))
     ? channel_count_++
-    :channel_map.size ();
+    : channel_map.size ();
 
   /* MIDI players tend to ignore instrument settings on channel
      10, the percussion channel.  */
@@ -240,10 +246,14 @@ Staff_performer::acknowledge_audio_element (Audio_element_info inf)
       string voice;
       if (c->is_alias (ly_symbol2scm ("Voice")))
 	voice = c->id_string ();
+      SCM channel_mapping = get_property ("midiChannelMapping");
+      if (channel_mapping == ly_symbol2scm ("voice"))
+	channel_ = get_channel (voice);
       string str = new_instrument_string ();
       if (str.length ())
 	{
-	  channel_ = get_channel (str);
+	  if (channel_mapping != ly_symbol2scm ("voice"))
+	    channel_ = get_channel (str);
 	  set_instrument (channel_, voice);
 	  set_instrument_name (voice);
 	}
diff --git a/ly/performer-init.ly b/ly/performer-init.ly
index 0b9a18f34b..1b9e18665a 100644
--- a/ly/performer-init.ly
+++ b/ly/performer-init.ly
@@ -137,6 +137,7 @@
 
   melismaBusyProperties = #default-melisma-properties
   instrumentName = #"bright acoustic"
+  midiChannelMapping = #'instrument
 
   %% quarter = 60
   tempoWholesPerMinute = #(ly:make-moment 15 1)
diff --git a/scm/define-context-properties.scm b/scm/define-context-properties.scm
index 046ac2e4f3..439f68a72e 100644
--- a/scm/define-context-properties.scm
+++ b/scm/define-context-properties.scm
@@ -357,8 +357,7 @@ half staff-spaces.  Usually determined by looking at
 @code{midiMinimumVolume}.")
      (midiMinimumVolume ,number? "Set the minimum loudness for MIDI.
 Ranges from 0 to@tie{}1.")
-     (midiChannelPerStaff ,boolean? "If set to @code{##t},
-each staff is assiged its own channel.")
+     (midiChannelMapping ,symbol? "How to map MIDI channels: per @code{instrument} (default), @code{staff} or @code{voice}.")
      (minimumFret ,number? "The tablature auto string-selecting
 mechanism selects the highest string with a fret at least
 @code{minimumFret}.")
diff --git a/scripts/midi2ly.py b/scripts/midi2ly.py
index a59cadcbd6..f0c64358c4 100644
--- a/scripts/midi2ly.py
+++ b/scripts/midi2ly.py
@@ -981,7 +981,11 @@ def convert_midi (in_file, out_file):
         if context:
             s += '    \\context %(context)s=%(staff_name)s \\%(track_name)s\n' % locals ()
         i += 1
-    s = s + '  >>\n}\n'
+    s = s + '''  >>
+  \layout {}
+  \midi {}
+}
+'''
 
     progress (_ ("%s output to `%s'...") % ('LY', out_file))
 
-- 
2.39.2