Great Downloader easy to use can convert into multiple file formats. Fast and impressive
FLAC - A free, open source codec for lossless audio compression and decompression
Video DownloadHelper - Browser extension to download videos from the Web
Opus Interactive Audio Codec - Opus is a totally open, royalty-free, highly versatile audio codec.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
Vorbis - Ogg Vorbis is a fully open, general-purpose compressed audio format for mid to high quality...
Youtube Video and Audio Downloader - Download YouTube videos in all available formats and extract the original audio files.