MediaHuman YouTube to MP3 Converter - Extracts MP3 audio from YouTube, Vimeo, Dailymotion, Mixcloud, Bandcamp, SoundCloud and many others. Available for macOS, Windows and Ubuntu/Linux. FREE!
4k Video Downloader - 4K Video Downloader is a software program that helps people download video files from sites such as Facebook, YouTube and Dailymotion.
YTmp3.net - Download your favorite YouTube videos as mp3 files without registration.
Youtube Video and Audio Downloader - Download YouTube videos in all available formats and extract the original audio files.
OnlineVideoConverter.com - OnlineVideoConverter.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.