I use 4K Downloader to download videos and music to use in non-profit activities, like church lessons.  It is has an easy user-interface, reliably downloads music and videos, and does not spam with ads.  I highly recommend it.  

​You can download it here: 
​https://www.4kdownload.com/products/product-videodownloader?r=free_license https://www.4kdownload.com/products/product-youtubetomp3?r=free_license https://www.4kdownload.com/products/product-stogram?r=free_license