Chordify - Chordify turns any music or song (YouTube, Deezer, SoundCloud, MP3) into chords.
ChordU - Extracts chords from any song, integrated YouTube.
Riffstation - The web version is Free and you can learn how to play Chords with Youtube Songs.
AudioRetoucher - AudioRetoucher is a tool for analyzing music, changing tempo and pitch in real time
Transcribe - An online app that reduces the pain of converting audio & video to text. Saves thousands of hours every month for journalists, lawyers, students and professional transcriptionists all over the world, including researchers in Antarctica.
MusicTrans - MusicTrans is a powerful learning tool for playing any song.