The following powershell script converts via VLC the MP4's in the current directory to WAV files. It doesn't like apostrophes in the filename. You'll need windows VLC to run via Powershell and you'll need to set the execution policy to "Unrestricted".

You can verify the execution policy setting by using the Get-ExecutionPolicy PowerShell command: get-executionpolicy

Then:

set-executionpolicy unrestricted

The following is the script, copy paste and save in notepad as "convertMP4toWav.ps1" or whatever you prefer.

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$outputExtension = ".wav"
$bitrate = 1411
$channels = 2

foreach($inputFile in get-childitem -recurse -Filter *.mp4)
{
$outputFileName = [System.IO.Path]::GetFileNameWithoutExtension($inputFile.FullName) + $outputExtension;
$outputFileName = [System.IO.Path]::Combine($inputFile.DirectoryName, $outputFileName);
$outputFileName = $outputFileName.Replace("'", "`'");

$programFiles = ${env:ProgramFiles(x86)};
if($programFiles -eq $null) { $programFiles = $env:ProgramFiles; }

$processName = $programFiles + "\VideoLAN\VLC\vlc.exe"

$fn = $($inputFile.FullName).Replace("'", "`'");

$processArgs = "-I dummy -vvv "$fn" --sout=#transcode{acodec="mp3",ab="$bitrate","channels=$channels"}:standard{access="file",mux="wav",dst="$outputFileName"} vlc://quit"

#echo $processArgs
start-process $processName $processArgs -wait
}

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Anyway with VideoDownloadHelper you can save youtube video's then convert to WAV file.

Links:

Pastebin: https://pastebin.com/AawVm8aK
VLC: https://www.videolan.org/vlc/download-windows.html
VideoDownloadHelper: https://addons.mozilla.org/en-US/firefox/addon/video-downloadhelper/