UltraStar Deluxe is a free and open source karaoke game inspired by the Singstar™ game available on the Playstation®. It allows up to six players to sing along with music using microphones in order to score points, depending on the pitch of the voice and the rhythm of singing.
Understandably, you might be wondering about the choice of video. I mean … Lady Gada? Well, turns out not that many people upload videos singing Pink Floyd on YouTube anymore :x
If the video is blocked in your country due to abusive copyright rules, then just search YouTube for more.