The present disclosure is directed at methods and systems for implementing and scoring a vocal improvisation feature in a music video game. This feature can allow players of music video games to sing improvised harmonies for a song using a microphone controller. The improvised harmonies can be musically consonant with a pre-authored melody track programmed into the music video game. The improvised harmonies can comprise pre-authored notes programmed into the pre-authored melody track, or can be generated by the music video game during run-time based on the pre-authored melody track. The music video game can also display guidelines visually showing permissible harmony tracks in relation to the pre-authored melody track.