如何从 Music21 制作的音乐中生成实时音频输出？

Question

如何从 Music21 制作的音乐中生成实时音频输出。如果做不到这一点，我如何通过开源软件从 Music21 制作的音乐中产生任何音频输出？感谢您的帮助。

Answer 1

如您所见，music21 并非设计为音乐播放系统，而是设计为嵌入到其他播放系统中或从系统中调用它们。我们不打算在播放系统上投入太多工作（因为硬件支持，我们是一个小型研究实验室，音乐分析方面的工作仍需完成等），但您的解决方案非常优雅，以至于现在作为music21.midi.realtime 模块包含在所有版本的music21（v1.1 后）中。下面是一个例子，它利用了 music21 动态分配具有不同弯音对象的 midi 通道以模拟微音播放（大多数 midi 播放的主要问题）的能力：

#  Set up a detuned piano 
#  (where each key has a random 
#  but consistent detuning from 30 cents flat to sharp)
#  and play a Bach Chorale on it in real time.

from music21 import *
import random
keyDetune = []
for i in range(0, 127):
    keyDetune.append(random.randint(-30, 30))

b = corpus.parse('bach/bwv66.6')
for n in b.flat.notes:
    n.microtone = keyDetune[n.midi]
sp = midi.realtime.StreamPlayer(b)
sp.play()

StreamPlayer 的 .play() 函数也可以使用 busyFunction 和 busyArgs 和 busyWaitMilliseconds 参数，它们指定一个函数，最多在每个 busyWaitMilliseconds 调用一个函数（如果您的系统较慢，可能会更多）。最后还有一个 endFunction 和 endArgs 将被调用，以防您想设置某种线程播放。 -- Myke Cuthbert（Music21 创作者）

Answer 2

这就是我发现的。这是一个适用于 Windows XP 的 python 脚本。除了music21，它还需要pygame。

# genPlayM21Score.py Generates and Plays 2 Music21 Scores "on the fly".
#
# see way below for source notes

from music21 import *

# we create the music21 Bottom Part, and do this explicitly, one object at a time.

n1 = note.Note('e4')
n1.duration.type = 'whole'
n2 = note.Note('d4')
n2.duration.type = 'whole'
m1 = stream.Measure()
m2 = stream.Measure()
m1.append(n1)
m2.append(n2)
partLower = stream.Part()
partLower.append(m1)
partLower.append(m2)

# For the music21 Upper Part, we automate the note creation procedure

data1 = [('g4', 'quarter'), ('a4', 'quarter'), ('b4', 'quarter'), ('c#5', 'quarter')]
data2 = [('d5', 'whole')]
data = [data1, data2]
partUpper = stream.Part()

def makeUpperPart(data):
    for mData in data:
        m = stream.Measure()
        for pitchName, durType in mData:
            n = note.Note(pitchName)
            n.duration.type = durType
            m.append(n)
        partUpper.append(m)
makeUpperPart(data)        

# Now, we can add both Part objects into a music21 Score object.  

sCadence = stream.Score()
sCadence.insert(0, partUpper)
sCadence.insert(0, partLower)

# Now, let's play the MIDI of the sCadence Score [from memory, ie no file  write necessary] using pygame

import cStringIO

# for music21 <= v.1.2:
if hasattr(sCadence, 'midiFile'):
   sCadence_mf = sCadence.midiFile
else: # for >= v.1.3:
   sCadence_mf = midi.translate.streamToMidiFile(sCadence)
sCadence_mStr = sCadence_mf.writestr()
sCadence_mStrFile = cStringIO.StringIO(sCadence_mStr)

import pygame

freq = 44100    # audio CD quality
bitsize = -16   # unsigned 16 bit
channels = 2    # 1 is mono, 2 is stereo
buffer = 1024    # number of samples
pygame.mixer.init(freq, bitsize, channels, buffer)

# optional volume 0 to 1.0
pygame.mixer.music.set_volume(0.8)

def play_music(music_file):
    """
    stream music with mixer.music module in blocking manner
    this will stream the sound from disk while playing
    """
    clock = pygame.time.Clock()
    try:
        pygame.mixer.music.load(music_file)
        print "Music file %s loaded!" % music_file
    except pygame.error:
        print "File %s not found! (%s)" % (music_file, pygame.get_error())
        return
    pygame.mixer.music.play()
    while pygame.mixer.music.get_busy():
        # check if playback has finished
        clock.tick(30)

# play the midi file we just saved
play_music(sCadence_mStrFile)

#============================

# now let's make a new music21 Score by reversing the upperPart notes
data1.reverse()
data2 = [('d5', 'whole')]
data = [data1, data2]
partUpper = stream.Part()
makeUpperPart(data)        
sCadence2 = stream.Score()
sCadence2.insert(0, partUpper)
sCadence2.insert(0, partLower)

# now let's play the new Score
sCadence2_mf = sCadence2.midiFile
sCadence2_mStr = sCadence2_mf.writestr()
sCadence2_mStrFile = cStringIO.StringIO(sCadence2_mStr)
play_music(sCadence2_mStrFile)



## SOURCE NOTES
## There are 3 sources for this mashup:

# 1. Source for the Music21 Score Creation http://web.mit.edu/music21/doc/html/quickStart.html#creating-notes-measures-parts-and-scores

# 2.  Source for the Music21 MidiFile Class Behaviour http://mit.edu/music21/doc/html/moduleMidiBase.html?highlight=midifile#music21.midi.base.MidiFile

# 3.  Source for the pygame player: http://www.daniweb.com/software-development/python/code/216979/embed-and-play-midi-music-in-your-code-python