3 Simple Steps to Download Music From YouTube to a SD Card
Visit YouTube and locate the video with the music you want to save. Click the "Share" button. Right-click the URL that appears and select "Copy."
Visit any free online YouTube conversion website, such as https://onlinevideoconverter.com/, convert to MP3.
Insert the SD card to the card reader. Next insert the card reader to laptop / PC. Copy the converted MP3 to the SD card reader.