You should only download YouTube videos when you have permission from the video owner. Read YouTube’s terms of service notice that downloading content without permission is strictly prohibited.
4K Download is a software-based video converter that works with YouTube, Vimeo, Soundcloud, VEVO and many other websites.
This tool allows you to convert videos to MP3 with a simple drag and drop. No registration is required and it’s quick and easy to receive your MP3 files. It’s a fast and reliable option!
There are options available for Mac and Windows software.