This free program allows you to download any video hosted on YouTube.
The program has a built-in search engine that lets you find a specific video by typing its name or a keyword, and clicking on the Search button. A list of the videos found will appear in the upper part of the interface. From there, you can drag the name of the video you want to download and drop it on the lower panel. The program will start downloading the video immediately. You can also choose to only listen to the audio track of the file by using the audio controls in the upper left corner of the interface. This way, you can listen to a file without the need of downloading it.
As you may know, the default format of YouTube files is .FLV. The program allows you to choose the format in which you want to download your files. You only need to right-click on the file's name in the upper panel and choose the "Download as" option; a list of formats will appear for you to choose the one that best suits your needs. This function lets you download only the sound track of the file, so you can transfer it to your music player to listen to it without the need to watch the images.