Copy code from basic_voice example as skeleton

https://github.com/Rapptz/discord.py/blob/v1.7.3/examples/basic_voice.py

.gitignore

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+venv

pyproject.toml

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+[tool.autopep8]
+indent-size=2
+max-line-length=160
+ignore = ["E402"]

requirements.txt

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+aiohttp==3.7.4.post0
+async-timeout==3.0.1
+attrs==21.2.0
+autopep8==1.5.7
+cffi==1.14.6
+chardet==4.0.0
+discord==1.7.3
+discord.py==1.7.3
+idna==3.2
+multidict==5.1.0
+pycodestyle==2.7.0
+pycparser==2.20
+PyNaCl==1.4.0
+six==1.16.0
+toml==0.10.2
+typing-extensions==3.10.0.2
+yarl==1.6.3
+youtube-dl==2021.6.6

src/bot.py

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+import asyncio
+
+import discord
+import youtube_dl
+
+from discord.ext import commands
+
+# Suppress noise about console usage from errors
+youtube_dl.utils.bug_reports_message = lambda: ''
+
+
+ytdl_format_options = {
+    'format': 'bestaudio/best',
+    'outtmpl': '%(extractor)s-%(id)s-%(title)s.%(ext)s',
+    'restrictfilenames': True,
+    'noplaylist': True,
+    'nocheckcertificate': True,
+    'ignoreerrors': False,
+    'logtostderr': False,
+    'quiet': True,
+    'no_warnings': True,
+    'default_search': 'auto',
+    'source_address': '0.0.0.0'  # bind to ipv4 since ipv6 addresses cause issues sometimes
+}
+
+ffmpeg_options = {
+    'options': '-vn'
+}
+
+ytdl = youtube_dl.YoutubeDL(ytdl_format_options)
+
+
+class YTDLSource(discord.PCMVolumeTransformer):
+  def __init__(self, source, *, data, volume=0.5):
+    super().__init__(source, volume)
+
+    self.data = data
+
+    self.title = data.get('title')
+    self.url = data.get('url')
+
+  @classmethod
+  async def from_url(cls, url, *, loop=None, stream=False):
+    loop = loop or asyncio.get_event_loop()
+    data = await loop.run_in_executor(None, lambda: ytdl.extract_info(url, download=not stream))
+
+    if 'entries' in data:
+      # take first item from a playlist
+      data = data['entries'][0]
+
+    filename = data['url'] if stream else ytdl.prepare_filename(data)
+    return cls(discord.FFmpegPCMAudio(filename, **ffmpeg_options), data=data)
+
+
+class Music(commands.Cog):
+  def __init__(self, bot):
+    self.bot = bot
+
+  @commands.command()
+  async def join(self, ctx, *, channel: discord.VoiceChannel):
+    """Joins a voice channel"""
+
+    if ctx.voice_client is not None:
+      return await ctx.voice_client.move_to(channel)
+
+    await channel.connect()
+
+  @commands.command()
+  async def play(self, ctx, *, query):
+    """Plays a file from the local filesystem"""
+
+    source = discord.PCMVolumeTransformer(discord.FFmpegPCMAudio(query))
+    ctx.voice_client.play(source, after=lambda e: print('Player error: %s' % e) if e else None)
+
+    await ctx.send('Now playing: {}'.format(query))
+
+  @commands.command()
+  async def yt(self, ctx, *, url):
+    """Plays from a url (almost anything youtube_dl supports)"""
+
+    async with ctx.typing():
+      player = await YTDLSource.from_url(url, loop=self.bot.loop)
+      ctx.voice_client.play(player, after=lambda e: print('Player error: %s' % e) if e else None)
+
+    await ctx.send('Now playing: {}'.format(player.title))
+
+  @commands.command()
+  async def stream(self, ctx, *, url):
+    """Streams from a url (same as yt, but doesn't predownload)"""
+
+    async with ctx.typing():
+      player = await YTDLSource.from_url(url, loop=self.bot.loop, stream=True)
+      ctx.voice_client.play(player, after=lambda e: print('Player error: %s' % e) if e else None)
+
+    await ctx.send('Now playing: {}'.format(player.title))
+
+  @commands.command()
+  async def volume(self, ctx, volume: int):
+    """Changes the player's volume"""
+
+    if ctx.voice_client is None:
+      return await ctx.send("Not connected to a voice channel.")
+
+    ctx.voice_client.source.volume = volume / 100
+    await ctx.send("Changed volume to {}%".format(volume))
+
+  @commands.command()
+  async def stop(self, ctx):
+    """Stops and disconnects the bot from voice"""
+
+    await ctx.voice_client.disconnect()
+
+  @play.before_invoke
+  @yt.before_invoke
+  @stream.before_invoke
+  async def ensure_voice(self, ctx):
+    if ctx.voice_client is None:
+      if ctx.author.voice:
+        await ctx.author.voice.channel.connect()
+      else:
+        await ctx.send("You are not connected to a voice channel.")
+        raise commands.CommandError("Author not connected to a voice channel.")
+    elif ctx.voice_client.is_playing():
+      ctx.voice_client.stop()
+
+
+bot = commands.Bot(command_prefix=commands.when_mentioned_or("!"),
+                   description='Relatively simple music bot example')
+
+
+@bot.event
+async def on_ready():
+  print('Logged in as {0} ({0.id})'.format(bot.user))
+  print('------')
+
+bot.add_cog(Music(bot))
+bot.run('token')