The author mentions just downloading the audio track. That's a lot less data than downloading any video at all. ;)
Oh, I missed that! In that case,
yt-dlp -x <url>
.. or optionally to convert it to mp3 on the fly: yt-dlp -x --audio-format mp3 <url>
.. or doing so with also the best audio quality available: yt-dlp -f 'ba' -x --audio-format mp3 <url>