Allow the user to specify the channel. Useful to use channel 10 for p…

…ercussion.

demo_tracks.py

@@ -1,7 +1,7 @@
 from pyknon.genmidi import Midi
 from pyknon.music import NoteSeq
 
-# Notes on two tracks
+# Notes on two tracks using the defaults
 
 notes1 = NoteSeq("C4.'' B8' A4 D")
 notes2 = NoteSeq("E4 F G4. A8")
@@ -11,7 +11,7 @@
 m.seq_notes(notes2, track=1)
 m.write("tracks.mid")
 
-# Chords on two tracks
+# Chords on two tracks using the defaults
 
 chords1 = [NoteSeq("C2 E G"), NoteSeq("G2 B D")]
 chords2 = [NoteSeq("C,4 E"), NoteSeq("E, G"), NoteSeq("G, B"), NoteSeq("B, D'")]
@@ -20,3 +20,18 @@
 midi.seq_chords(chords1, track=0)
 midi.seq_chords(chords2, track=1)
 midi.write("chords.mid")
+
+# Notes on two tracks using percussion
+
+# In the MIDI library, the tracks and channels are numbered from 0,
+# While the MIDI Standard is numbered from 1,
+# So to use percussion you must use channel 9 in the library
+
+n1 = NoteSeq("C4 D E F")
+n2 = NoteSeq("C8 C G, G C' C G, G")
+
+m2 = Midi(2, tempo=123, channel=[0, 9], instrument=[20, 40])
+m2.seq_notes(n1, track=0, channel=0)
+m2.seq_notes(n2, track=1, channel=9)
+m2.write("percussion.mid")
+

pyknon/genmidi.py

@@ -7,47 +7,55 @@ class MidiError(Exception):
 
 
 class Midi(object):
-    def __init__(self, number_tracks=1, tempo=60, instrument=0):
+    def __init__(self, number_tracks=1, tempo=60, instrument=0, channel=None):
         """
         instrument: can be an integer or a list
+        channel: can be an integer or a list
         """
 
         self.number_tracks = number_tracks
         self.midi_data = MIDIFile(number_tracks)
 
         for track in range(number_tracks):
-            channel = track
             self.midi_data.addTrackName(track, 0, "Track {0}".format(track))
             self.midi_data.addTempo(track, 0, tempo)
             instr = instrument[track] if isinstance(instrument, list) else instrument
-            self.midi_data.addProgramChange(track, channel, 0, instr)
+            if channel is None:
+                _channel = track
+            elif isinstance(channel, list):
+                _channel = channel[track]
+            else:
+                _channel = channel
+            self.midi_data.addProgramChange(track, _channel, 0, instr)
 
-    def seq_chords(self, seqlist, track=0, time=0):
+    def seq_chords(self, seqlist, track=0, time=0, channel=None):
         if track + 1 > self.number_tracks:
             raise MidiError("You are trying to use more tracks than we have.")
 
-        channel = track
+        _channel = channel if channel is not None else track
+
         for item in seqlist:
             if isinstance(item, NoteSeq):
                 volume = item[0].volume
                 dur = item[0].midi_dur
                 for note in item:
-                    self.midi_data.addNote(track, channel, note.midi_number, time, dur, volume)
+                    self.midi_data.addNote(track, _channel, note.midi_number, time, dur, volume)
                 time += dur
             elif isinstance(item, Rest):
                 time += item.midi_dur
             else:
                 raise MidiError("The input should be a list of NoteSeq but yours is a {0}: {1}".format(type(seqlist), seqlist))
         return time
 
-    def seq_notes(self, noteseq, track=0, time=0):
+    def seq_notes(self, noteseq, track=0, time=0, channel=None):
         if track + 1 > self.number_tracks:
             raise MidiError("You are trying to use more tracks than we have.")
 
-        channel = track
+        _channel = channel if channel is not None else track
+
         for note in noteseq:
             if isinstance(note, Note):
-                self.midi_data.addNote(track, channel, note.midi_number, time, note.midi_dur, note.volume)
+                self.midi_data.addNote(track, _channel, note.midi_number, time, note.midi_dur, note.volume)
             else:
                 # we ignore the rests
                 pass