【Day18】在 Python 里头利用 Mido 进行编曲

Message in MIDI

书接昨日，在 MIDI 里面有固定的格式在记录声音的讯号，因为实在是太多了我们不会一一举例，这边只说明几个常用到的，完整的官方文件请参照这里

1.Program change
用於更改不同 channel 的乐器音色

    Message('program_change',channel,id,time =0)

channel 为 0 ~ 15，更改这个值来更改声音的通道，MIDI 默认有 16 个通道
id 是乐器的编号，你可以在这里查到，总共有 128 种

Note on
音符的开始

Message('note_on',note,vel,time,channel)

note 值为 0~127，代表音高，比方说 60 就对应到 C4
vel 值为 0~127，代表声音的强度，默认是 64
time 的意思是 "这个音符要在前一个音符结束後过多久开始"

Note off
音符的结束，通常紧跟在 Note on 後面
```
 Message('note_off',note,vel,time,channel)
```
Control change (cc)
控制声音，比方说踩钢琴的延音踏板这类的操作
```
 Message('control_change',channel,control,value,time)
```

control 可以选择要对声音做哪些奇妙操作，详细请参考这篇，这里列几个常用到的操作
1. 64 - 延音踏版
2. 71 - Harmonic Intens. 共鸣,可以控制声音较突显或隐诲
3. 72 - Release Time 音符结束之後,声音渐弱至完全没有的时间
4. 73 - Attack Time 音符开始之後,从无声爬到至最高点的时间
5. 74 - Brightness 调整声音的明亮度
value 则是控制实际操作的程度，比方说踩延音踏版这件事在 value =< 63 是 off 反之则是 on

开始编曲吧!

我们试着来编追追追 ~

from mido import Message, MidiFile, MidiTrack
mid = MidiFile()
track = MidiTrack()

 def play_part(track, note, len_ ,note_bias=0,vel=1.0,delay=0,change=False,double=False):
    # 每个节拍的时间长度
    temple = 60*60*10/75
    # 大调，参考别人的做法的，我也不是很懂乐理
    major_notes = [0,2,2,1,2,2,2,1]
    # C4 - 正中间的 DO
    base_note = 60
    bias = note_bias*12 + sum(major_notes[0:note])
    vel = round(64*vel)
    t_start = round(delay*temple)
    t_end =  round(temple*len_)
    if not double:
        track.append(Message("note_on",  note=base_note+bias,velocity=vel,time=t_start))
        track.append(Message("note_off", note=base_note+bias,velocity=vel,time=t_end))
    if change:
        track.append(Message("control_change",channel=0,control=64,value=64,time=t_start))
        track.append(Message("control_change",channel=0,control=64,value=0,time=t_end))
    if double:
        track.append(Message("program_change", channel=1,program=41 ,time = t_start))
        track.append(Message("note_on",channel=1, note=base_note+bias,velocity=vel,time = t_start))
        track.append(Message("note_off",channel=1, note=base_note+bias,velocity=vel,time = t_end))
        track.append(Message("program_change", channel=1,program=0 ,time=t_end))
    return track
    
    track = play_part(track,6,0.5)
    
######## 第一段 ###########

track = play_part(track,5,0.5)
track = play_part(track,6,0.5)
track = play_part(track,6,0.5)
track = play_part(track,5,0.5)
track = play_part(track,3,0.5)

track = play_part(track,2,0.5)
track = play_part(track,1,0.5)
track = play_part(track,2,0.5)
track = play_part(track,2,0.5)
track = play_part(track,1,0.5)
track = play_part(track,2,0.5)

track = play_part(track,2,0.5)
track = play_part(track,1,0.5)
track = play_part(track,2,0.5)
track = play_part(track,3,1.5)
track = play_part(track,5,0.5)
track = play_part(track,2,0.5)

track = play_part(track,3,1.0,change=True)

track = play_part(track,3,0.25,double=True)
track = play_part(track,5,0.25,double=True)
track = play_part(track,2,0.25,double=True)


######## 第二段 ###########

track = play_part(track,3,0.5)
track = play_part(track,6,0.5)
track = play_part(track,5,0.5)
track = play_part(track,2,0.5)
track = play_part(track,5,0.5)
track = play_part(track,2,0.5)

track = play_part(track,6,0.5,-1)
track = play_part(track,2,0.5)
track = play_part(track,1,0.5)
track = play_part(track,6,0.5,-1)
track = play_part(track,2,0.5)
track = play_part(track,2,0.5)

track = play_part(track,2,0.5)
track = play_part(track,5,1.5)
track = play_part(track,2,0.5)
track = play_part(track,2,0.5)
track = play_part(track,3,0.25)
track = play_part(track,5,0.25)


track = play_part(track,5,1.5)
track = play_part(track,5,0.5,-1)
track = play_part(track,5,0.5,-1)

track = play_part(track,6,0.5,-1)
track = play_part(track,6,1.0,-1,change=True)

track = play_part(track,5,0.5,-1,double=True)
track = play_part(track,6,0.5,-1,double=True)
track = play_part(track,6,1.5,-1,double=True)

######## 剩下的请加油 XD ###########

mid.tracks.append(track)
mid.save('new_song.mid')