This is an interface I made for youtube-dl because I didn't want to have to remember all the arguments or type them in when I wanted some music to put on my phone.
You will need youtube-dl (provided in Executables folder), which can be downloaded from here and ffmpeg, which can be downloaded from here. There is an update youtube-dl button in the GUI, to save you some hassle.
You enter a URL at the top, and press start to begin downloading! There is a button to open the folder where the file downloaded to so you don't have to find it yourself. If you want to specify an existing folder to download into, you can do that either by pasting the folder path into the Folder textbox or by browsing for the folder. Anything more complicated than that is found under the "Advanced options" tab.
While everything has text that explains what it does if you hover over it, here is an explanation of some of the things. If youtube-dl is called something else in your system, then there is a box called "Program name" where you can enter the correct name. If you want the opened command window to remain open after youtube-dl finishes (useful if there was an error and you need to read it), you can enable that. If you want to keep the downloaded video files that are usually deleted after conversion to audio, you can opt to keep them through the "Keep original files" checkbox.
I did NOT make youtube-dl, ffmpeg or any other associated program. I have simply made an interface for these programs.