UltraStar is a freeware music video game developed by Loud Arts and is based on the commercial SingStar series. The main objective is to sing along to the song or music video (with the song lyrics displayed) and score points by matching the pitch and timing of the song. UltraStar is very customisable as you can add your own songs, lyrics, backdrop image and even a music video.
Mac OS X 10.5 or newer
Intel powered Mac
OpenGL graphics card
Free download at sourceforge.com