userguide/02.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 用户指南，第2章：音符\n",
    "[原文链接](https://web.mit.edu/music21/doc/usersGuide/usersGuide_02_notes.html)\n",
    "\n",
    "符号音乐（Notated music），顾名思义，由一系列在时间上先后出现的音符（note）组成。除此之外，符号音乐还包含谱号，调号，连音符等其他信息。但是，音符是符号音乐的核心。所以，在开始探索music21前，先介绍music21如何处理音符。\n",
    "\n",
    "打开IDLE，或者在命令行输入`python`以开始。\n",
    "\n",
    "## 创建与处理音符\n",
    "music21中，一个标准的音符由`music21.note.Note`对象表示\n",
    "\n",
    "**Python新手请注意**（其他用户可跳过）：模块名和对象名不同。Python模块（可含有一个，多个，或不含有对象），永远以小写字母开头。Music21的对象以大写字母开头。所以，`Note`对象包含在`note`模块中。Python严格区分大小写。\n",
    "\n",
    "note模块中还有其他类。最重要的是`note.Rest`，表示休止符。\n",
    "\n",
    "用以下命令载入music21库:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "from music21 import *"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "然后即可输入`note`，以访问`note`模块"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<module 'music21.note' from 'E:\\\\Python39\\\\lib\\\\site-packages\\\\music21\\\\note.py'>"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "note"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "如果想知道note模块中还有哪些内容，输入`dir(note)`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['GeneralNote',\n",
       " 'Lyric',\n",
       " 'LyricException',\n",
       " 'NotRest',\n",
       " 'NotRestException',\n",
       " 'Note',\n",
       " 'NoteException',\n",
       " 'Rest',\n",
       " 'SYLLABIC_CHOICES',\n",
       " 'Unpitched',\n",
       " 'base',\n",
       " 'beam',\n",
       " 'common',\n",
       " 'duration',\n",
       " 'environLocal',\n",
       " 'environment',\n",
       " 'exceptions21',\n",
       " 'expressions',\n",
       " 'interval',\n",
       " 'noteheadTypeNames',\n",
       " 'pitch',\n",
       " 'prebase',\n",
       " 'stemDirectionNames',\n",
       " 'style',\n",
       " 'tie',\n",
       " 'volume']"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dir(note)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这个列表中的部分内容是音符类。其他类我们后面将会介绍，例如Lyric对象。\n",
    "\n",
    "### (题外话)\n",
    "\n",
    "如果害怕污染命名空间，可以输入："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [],
   "source": [
    "import music21"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "那么，你需要用`music21.note`来访问note类（而不是`note`）"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<module 'music21.note' from 'E:\\\\Python39\\\\lib\\\\site-packages\\\\music21\\\\note.py'>"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "music21.note"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### （回归正题）\n",
    "创建一个音高为F5的note.Note对象"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [],
   "source": [
    "f=note.Note(\"F5\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "music21中，中央C是C4，比它高一个八度的是C5。\n",
    "\n",
    "现在你有了一个音符，它在哪里？它储存在变量f里面。输入`f`即可访问"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<music21.note.Note F>"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "用`.name`和`.octave`，可以确认，它确实是第5个八度上的F"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'F'"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.name"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "5"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.octave"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Note的另一个属性是音高`.pitch`，它返回一个`Pitch`对象"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<music21.pitch.Pitch F5>"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.pitch"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Pitch对象能够获取关于音高的更多信息，例如频率`.frequency`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "698.456462866008"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.pitch.frequency"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "还有`.pitchClassString`（字符串形式的八度编号）"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'5'"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.pitch.pitchClassString"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "所以，f是大约698hz（如果A4=440hz），而且是第5八度（C=0，C#=D-=1，依此类推）\n",
    "\n",
    "需要注意到几点：\n",
    "1. 你的电脑显示的`frequency`可能比本文档拥有更多的小数位数。在本文档中，我们有时候会写\"...\"，而不是列出所有小数位数。这是因为，数字的长度，甚至最后几位数的具体数值，会随python位数为32位或64位，系统为Mac或Windows而异。得到略微不同的结果是正常现象。\n",
    "2. 有些输出是用单引号包住的（像`f.name`的`'F'`），另一些没有单引号（像`f.octave`的`5`）。有单引号的输出说明返回值是字符串，没有单引号说明返回值是数值（要么是整数，要么，如果有小数点的话，一个卑鄙地模仿小数的东西，叫做浮点数`float`。它大部分看起来，表现起来都像个小数，但有时又不像，你永远预测不到）\n",
    "   \n",
    "*(说到`float`背后的历史和原理，任何一个计算机科学家都能和你讲上一大箩筐，通常当ta是站在你和吧台之间的唯一一样东西的时候。真的，我们不应该继续用`float`，除非考虑到我们的电脑算`float`远快于算`decimal`)*\n",
    "\n",
    "> 译注：上面这一段是原作者关于二进制浮点数`float`的暴论，很大可能来源于工程实践中的以讹传讹。而我认为，如果浮点数真这么一无是处的话，像Python这种以降低使用难度为核心设计思想，并愿意为之牺牲性能的编程语言，就不会把`float`作为基本类型了，而是采用`decimal`作为基本类型，把`float`作为高性能计算的扩展类型。况且，本案例中的频率是无理数，即便用十进制浮点数`decimal`也无法精确表示。而对于绝大多数使用场景来说，`float`的精度绰绰有余。所以，我们大可放心使用`float`，并**仅**在需要使数值**精确地等于一个十进制小数**时，才做特殊处理，例如用整型的123分来表示1.23元。\n",
    "> \n",
    "> 关于这一话题的更多讨论，参见这个[知乎问题](https://www.zhihu.com/question/65960911/answer/237638982)\n",
    "\n",
    "字符串`'5'`和数值`5`不一样。在Python中，我们用双等号（`==`）来判断两个对象是否“相等”。所以"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.octave==5"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "结果正如我们所预料。但是"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 14,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.pitch.pitchClassString == 5"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这是由于在Python语言中，数值`5`和字符串`\"5\"`不相等。（有些编程语言，例如JavaScript和Perl认为它们相等，但Python不是。一开始你可能会觉得这不方便，但是随着学习的深入，你会发现这一设计的好处）。\n",
    "\n",
    "所以，如果要判断`f.pitchClassString`是`'5'`，我们要用引号把它变成字符串："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.pitch.pitchClassString == \"5\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python中，用单引号和双引号来表示字符串都可以"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.pitch.pitchClassString == '5'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`pitchClassString`这个名字告诉你，它输出的应该是个字符串。另有一个`pitchClass`输出的是数值："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "5"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.pitch.pitchClass"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "对于音高`F`来说，这两种获取pitch class的方式返回了大致相同的结果，唯一区别是：一个是整数，一个是字符串。但是对于`B-`来说，`pitchClass`是10，而`pitchClassString`是`\"A\"`，是不同的。\n",
    "\n",
    "我们来创建一个`B-`音符。在music21中，升调符号是`\"#\"`。但是，降调符号是`\"-\"`而不是`\"b\"`。这是因为`\"b\"`会与音名`\"b\"`冲突。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [],
   "source": [
    "bflat = note.Note(\"B-2\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这里我把它命名为`bflat`。你也可以把它命名为`Bb`或者`b_flat`，但不能叫做`b-flat`，因为变量名不允许出现减号："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "cannot assign to operator (Temp/ipykernel_7120/2736611904.py, line 1)",
     "output_type": "error",
     "traceback": [
      "\u001b[1;36m  File \u001b[1;32m\"C:\\Users\\lin\\AppData\\Local\\Temp/ipykernel_7120/2736611904.py\"\u001b[1;36m, line \u001b[1;32m1\u001b[0m\n\u001b[1;33m    b-flat = note.Note(\"B-2\")\u001b[0m\n\u001b[1;37m    ^\u001b[0m\n\u001b[1;31mSyntaxError\u001b[0m\u001b[1;31m:\u001b[0m cannot assign to operator\n"
     ]
    }
   ],
   "source": [
    "#取消注释以运行以下代码\n",
    "#b-flat = note.Note(\"B-2\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这个音符有变调符号，我们可以用`.pitch.accidental`来获取"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<music21.pitch.Accidental flat>"
      ]
     },
     "execution_count": 20,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "bflat.pitch.accidental"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "现在我们得到了一个不是数值，但又没有引号的东西。这通常说明它是一个对象（在这里是`Accidental`对象）。正如我们上面介绍的，对象具有属性，`Accidental`也不例外。我们把`bflat`的变调符号另存为一个新的变量："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [],
   "source": [
    "acc = bflat.pitch.accidental"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "用`.alter`获取这个`Accidental`对象的半音数"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "-1.0"
      ]
     },
     "execution_count": 22,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "acc.alter"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`alter`是一个浮点数，说明music21可能支持微分音\n",
    "\n",
    "刚才两行，我们先定义了`acc`为`bflat.pitch.accidental`，然后获取`acc`的`alter`属性。其实我们可以合并为一步"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "-1.0"
      ]
     },
     "execution_count": 23,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "bflat.pitch.accidental.alter"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'normal'"
      ]
     },
     "execution_count": 24,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "acc.displayLocation"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Good to know that we’ve set a sensible default. If you want to have the accidental display above the note, you’ll have to set that yourself:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'above'"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "acc.displayLocation = 'above'\n",
    "acc.displayLocation"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "变量`acc`**就是**那个`bflat`音符下的`accidental`属性。（用计算机的术语来说，`acc`是`bflat.accidental`的一个“引用”）。现在我们回到`bflat.pitch.accidental`的`displayLocation`，我们会发现它也变了"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'above'"
      ]
     },
     "execution_count": 26,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "bflat.pitch.accidental.displayLocation"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python的一个特性是：如果一个对象不具有某个属性，你可以给它加上（有些人认为这会让对象变得混乱，但我无所谓）。例如，`bflat`没有`wasWrittenByStockhausen`属性，访问时会报错"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [
    {
     "ename": "AttributeError",
     "evalue": "'Note' object has no attribute 'wasWrittenByStockhausen'",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[1;32m~\\AppData\\Local\\Temp/ipykernel_7120/2960409618.py\u001b[0m in \u001b[0;36m<module>\u001b[1;34m\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0mbflat\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mwasWrittenByStockhausen\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m: 'Note' object has no attribute 'wasWrittenByStockhausen'"
     ]
    }
   ],
   "source": [
    "#取消注释以运行以下代码\n",
    "#bflat.wasWrittenByStockhausen"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "但如果你给它加上，那么就可以在后续代码中使用"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {},
   "outputs": [],
   "source": [
    "bflat.wasWrittenByStockhausen = True\n",
    "f.wasWrittenByStockhausen = False"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "然后你可以访问这个属性"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hope you're enjoying Sirius!\n"
     ]
    }
   ],
   "source": [
    "if bflat.wasWrittenByStockhausen == True:\n",
    "    print(\"Hope you're enjoying Sirius!\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "注意：刚才这一行，你需要在开头加入几个空格，因为python用缩进来给代码划分层次。\n",
    "\n",
    "（如果你没get到Stockhausen梗，请查看[维基百科](https://wanweibaike.net/wiki-%E5%8D%A1%E5%B0%94%E6%B5%B7%E5%9B%A0%E8%8C%A8%C2%B7%E6%96%BD%E6%89%98%E5%85%8B%E8%B1%AA%E6%A3%AE)）\n",
    "\n",
    "而对于音符`f`，由于我们把`f.wasWrittenByStockhausen`设为`False`，则以下代码不会输出任何内容："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {},
   "outputs": [],
   "source": [
    "if f.wasWrittenByStockhausen == True:\n",
    "    print(\"I love Helicopters!\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "到现在为止，你可能已经厌烦了，想马上看到或听到音符。如果你已经安装了一个MusicXML阅读器，例如MuseScore，Finale，Sibelius，或者Dorico，可以输入："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "image/png": "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",
      "text/plain": [
       "<IPython.core.display.Image object>"
      ]
     },
     "metadata": {
      "image/png": {
       "height": 49,
       "width": 143
      }
     },
     "output_type": "display_data"
    }
   ],
   "source": [
    "f.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "即可看到它。音符的默认时长是四分音符。后面我们会教你设定其他的音符时长。注意乐谱中的谱号，否则你不知道这个音符确实是`F5`\n",
    "\n",
    "如果你想听到它（而且你用的是Windows或Unix或旧版Mac（10.5及以下）），输入："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "\n",
       "                <div id='midiPlayerDiv68'></div>\n",
       "                <link rel=\"stylesheet\" href=\"//cuthbertLab.github.io/music21j/css/m21.css\"\n",
       "                    type=\"text/css\" />\n",
       "                <script>\n",
       "                require.config({\n",
       "                    paths: {'music21': '//cuthbertLab.github.io/music21j/src/music21'}\n",
       "                });\n",
       "                require(['music21'], function() {\n",
       "                               mp = new music21.miditools.MidiPlayer();\n",
       "                               mp.addPlayer('#midiPlayerDiv68');\n",
       "                               mp.base64Load('data:audio/midi;base64,TVRoZAAAAAYAAQACBABNVHJrAAAAFAD/UQMHoSAA/1gEBAIYCIgA/y8ATVRyawAAABcA/wMAAOAAQIgAkE1aiACATQCIAP8vAA==');\n",
       "                        });\n",
       "                </script>"
      ],
      "text/plain": [
       "<IPython.core.display.HTML object>"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "f.show('midi')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "使用`f.octave`时不需要括号，但调用`f.show()`时必须要一对括号，即使里面没有内容也要有括号（这种情况下，music21会采用默认模式显示音符，通常是`musicxml`）\n",
    "\n",
    "`.show()`是`Note`对象的一个方法，而`.octave`是属性。调用方法时必须带括号，括号里面可以输入一些其他变量（称为参数）来控制这个方法。例如，把`bflat`升高大三度："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<music21.note.Note D>"
      ]
     },
     "execution_count": 33,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "d = bflat.transpose(\"M3\")\n",
    "d"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<music21.note.Note B->"
      ]
     },
     "execution_count": 34,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "bflat"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`transpose()`方法不会改变原来的音符，而是返回一个新音符对象作为移调操作的结果。\n",
    "\n",
    "如果想就地修改`bflat`对象，可以加入`inPlace = True`参数："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<music21.note.Note E->"
      ]
     },
     "execution_count": 35,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "bflat.transpose(\"P4\", inPlace=True)\n",
    "bflat"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "那么现在`bflat`成为了一个糟糕的变量名。你可以输入`eflat=bflat`，但你也可以不这么频繁地做这件事。\n",
    "\n",
    "顺便说一下，music21支持一些非常奇葩的音程。例如，将`d`升高一个减减六度："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<music21.note.Note B--->"
      ]
     },
     "execution_count": 36,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "whatNoteIsThis = d.transpose('dd6')\n",
    "whatNoteIsThis"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "从未见过的`B---`！我们来查看这个音符的`.pitch.accidental.alter `和`.pitch.accidental.name`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 37,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "-3.0"
      ]
     },
     "execution_count": 37,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "whatNoteIsThis.pitch.accidental.alter"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 38,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'triple-flat'"
      ]
     },
     "execution_count": 38,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "whatNoteIsThis.pitch.accidental.name"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "最后一件事：不是所有音符都有变调符号，例如`d`就没有。所以d的`accidental`为`None`，它是一个不输出任何内容的特殊对象："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 39,
   "metadata": {},
   "outputs": [],
   "source": [
    "d.pitch.accidental"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "如果你要确认它是None，请输入："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 40,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "None\n"
     ]
    }
   ],
   "source": [
    "print(d.pitch.accidental)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "既然`d.accidental`是`None`，那么`d.accidental.name`也是`None`吗？"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 41,
   "metadata": {},
   "outputs": [
    {
     "ename": "AttributeError",
     "evalue": "'NoneType' object has no attribute 'name'",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[1;32m~\\AppData\\Local\\Temp/ipykernel_7120/1250031737.py\u001b[0m in \u001b[0;36m<module>\u001b[1;34m\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0md\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mpitch\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0maccidental\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mname\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m: 'NoneType' object has no attribute 'name'"
     ]
    }
   ],
   "source": [
    "#取消注释以运行以下代码\n",
    "#d.pitch.accidental.name"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "不是，而是产生一个错误。这是由于`None`不是`Accidental`对象，而是`NoneType`对象，而它没有`name`属性。\n",
    "\n",
    "如果在交互式命令行写代码，产生一个错误是小事，但如果这段代码在一个大程序中运行，则错误通常会导致程序崩溃。所以我们要确保音符有`Accidentals`属性，才显示它的名称"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "metadata": {},
   "outputs": [],
   "source": [
    "if d.pitch.accidental is not None:\n",
    "    print(d.pitch.accidental.name)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这种方法更安全，因为我们只在`d.pitch.accidental`不是`None`时，才输出`d.pitch.accidental.name`。由于刚才它是`None`，Python就不会运行第二行代码。\n",
    "\n",
    "如果因为某种原因，`d`没有`pitch`属性，我们可能也要测试它是不是`None`，然后才能使用`.pitch.accidental`\n",
    "\n",
    "例如休止符`Rest`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 43,
   "metadata": {},
   "outputs": [],
   "source": [
    "r = note.Rest()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "记得在创建`note.Rest`时带一对括号，否则会发生奇怪的事情。\n",
    "\n",
    "同样用`.show()`查看"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "image/png": "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",
      "text/plain": [
       "<IPython.core.display.Image object>"
      ]
     },
     "metadata": {
      "image/png": {
       "height": 49,
       "width": 146
      }
     },
     "output_type": "display_data"
    }
   ],
   "source": [
    "r.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "但是如果把它作为midi文件播放，休止符是没有声音的。\n",
    "\n",
    "`Rest`对象没有`pitch`属性，所以也没有`.pitch.accidental`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "metadata": {},
   "outputs": [
    {
     "ename": "AttributeError",
     "evalue": "'Rest' object has no attribute 'pitch'",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[1;32m~\\AppData\\Local\\Temp/ipykernel_7120/3759757543.py\u001b[0m in \u001b[0;36m<module>\u001b[1;34m\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0mr\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mpitch\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m: 'Rest' object has no attribute 'pitch'"
     ]
    }
   ],
   "source": [
    "#取消注释以运行以下代码\n",
    "#r.pitch"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "最后一件事情：我们从未使用变量名`note`。**千万不要这样做**。如果你输入以下代码："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "metadata": {},
   "outputs": [],
   "source": [
    "note=note.Note(\"C#3\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "你把一个对象储存为`note`，但是又需要使用`note`模块来创建新的`Note`对象，而现在没办法访问`note`模块了（这就是“污染命名空间”）的后果。所以请不要用`note`作为变量名（`pitch`、`scale`、`key`、`clef`等同理，你可以使用`myNote`和`myClef`来避免）。\n",
    "\n",
    "下一章：[用户指南，第3章：音高，时长与音符](03.ipynb)"
   ]
  }
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