Python 写 MIDI 文件

Question

我想用从我连接的数码钢琴接收到的输入来编写一个 MIDI 文件。我正在使用 pygame.midi 打开一个输入端口并使用 midiutil 来编写 MIDI 文件。我无法理解的是时机。例如，在 addNote(track, channel, pitch, time, duration, volume) ，我怎么知道是什么time和 duration注意事项是？阅读音符时，我的音高和音量都很好，但其他的我不知道......我尝试使用时间戳但无济于事，它将音符放在 MIDI 文件中非常远的地方。
那么，我如何计算笔记的“时间”和“持续时间”？

Answer 1

time规定了音符应该在音乐时间中的位置。参数应该是什么部分取决于 Midi 文件对象的构造方式(稍后会详细介绍)
实际上，MIDI 要求每个音符有两条消息:a NOTE On消息和 NOTE Off信息。 duration将指示何时 Note Off消息应该被发送，相对于笔记的开始。同样，参数的形成方式取决于文件对象的构造方式。
来自 MIDIUtil docs :

• time – the time at which the note sounds. The value can be either quarter notes [Float], or ticks [Integer]. Ticks may be specified by passing eventtime_is_ticks=True to the MIDIFile constructor. The default is quarter notes.
• duration – the duration of the note. Like the time argument, the value can be either quarter notes [Float], or ticks [Integer]

演奏 C 大调音阶的完整示例

from midiutil import MIDIFile
degrees = [60, 62, 64, 65, 67, 69, 71, 72] # MIDI note number
track = 0
channel = 0
time = 0 # In beats
duration = 1 # In beats
tempo = 60 # In BPM
volume = 100 # 0-127, as per the MIDI standard
MyMIDI = MIDIFile(1) # One track, defaults to format 1 (tempo track
# automatically created)
MyMIDI.addTempo(track,time, tempo)
for pitch in degrees:
    MyMIDI.addNote(track, channel, pitch, time, duration, volume)
    time = time + 1
with open("major-scale.mid", "wb") as output_file:
    MyMIDI.writeFile(output_file)

组合文件tempo (在当前时间)结合笔记的位置( time )和 duration (就多少节拍而言)，库可以合成在正确时间播放(开始/停止)音符所需的所有 MIDI 消息。
另一个例子
让我们尝试将其应用于以下音乐短语:

首先，设置一切。

from midiutil import MIDIFile
track = 0
channel = 0
time = 0 # In beats
duration = 1 # In beats
tempo = 60 # In BPM
volume = 100 # 0-127, as per the MIDI standard
MyMIDI = MIDIFile(1) # One track, defaults to format 1 (tempo track
# automatically created)
MyMIDI.addTempo(track,time, tempo)

在 E 上添加前半音符和在 G 上添加四分音符:

time = 0  # it's the first beat of the piece
quarter_note = 1  # equal to one beat, assuming x/4 time
half_note = 2 # Half notes are 2x value of a single quarter note
E3 = 64  # MIDI note value for E3
G3 = 67

# Add half note
MyMIDI.addNote(track, channel, pitch=E3, duration=half_note, time=0, volume=volume)
# Add quarter note
MyMIDI.addNote(track, channel, pitch=G3, duration=quarter_note, time=0, volume=volume)

现在让我们添加剩余的注释:

A3 = 69
C3 = 60
B3 = 71
C4 = 72

# add the remaining notes
for time, pitch, duration in [(1,A3, quarter_note),
                              (2,B3, quarter_note), (2, C3, half_note), 
                              (3,C4, quarter_note)]:
    MyMIDI.addNote(track, channel, 
                   duration=duration, 
                   pitch=pitch, time=time, volume=volume)