Vocal harmony refers to singing where consonant notes are sung together by many voices. To create vocal harmony (or harmonize), a vocal melody is accompanied by a supplementary melody. Harmonizing can be done on top of a melody played by an instrument or the voice of other singers. As a singer, you can harmonize by singing either above or below the melody. Try doing this by singing a third or a whole octave up or down from the melody you're harmonizing to create vocal harmony.