Use this to download this category as MP3 with youtube-dl:
declare -a list=("https://www.youtube.com/channel/UCJvBEEqTaLaKclbCPgIjBSQ" "https://www.youtube.com/user/michelleheafy/videos" "https://www.youtube.com/channel/UCKW_hLWry2e3ZZbZZM3bD1g" "https://www.youtube.com/channel/UCDwMh0pu1iSXeKx7qmqjIQA/videos" "https://www.youtube.com/channel/UCftm4VNxngya7wjl_ZtLMPw/videos" "https://www.youtube.com/user/sh4dowww90/videos")
for val in ${list[@]}; do
name=$(basename "$val")
if [ -e $name ]
then
continue
fi
mkdir $name
cd $name
youtube-dl -f mp3-128 $val
cd ..
done