Add app.py and fixed hexachord

app.py

@@ -39,7 +39,7 @@ def create_midi(chords):
     for i_chord, chord in enumerate(chords):
         for i, note in enumerate(chord):
             if i == 0 and i_chord != 0:
-                track.append(Message('note_off', note=note.pitch.midi, velocity=0, time=1))
+                track.append(Message('note_on', note=note.pitch.midi, velocity=64, time=1))
             else:
                 track.append(Message('note_on', note=note.pitch.midi, velocity=64, time=0))
         for i, note in enumerate(chord):

hexachords.py

@@ -9,8 +9,6 @@ class Hexachord:
     def generate_chord_sequence(self, list_of_notes, intrvl="P5"):
 
         hexachord =  list_of_notes
-        s = stream.Stream()
-        s.append(hexachord)
         fifth = interval.Interval(intrvl)  # Perfect fifth
         all_pc = [n.pitch.pitchClass for n in hexachord]
         all_chords = []