For a vocalist to hit a note of this pitch, one's vocal cords must vibrate at over 4,000 times per second. This is nearly impossible because of the muscular control required in adducting the vocal cords that high. Adam Lopez, Nicola Sedda, Jacqueline Nix, and Georgia Brown have reached, and surpassed C8. Every octave jump doubles the rate of vibration (i.e. C5 vibrates twice as fast as middle C (C4) and soprano C (C6) two octaves higher than middle C vibrates four times as fast). The Guinness record for highest note sung by a male is now held by Adam Lopez, hitting E♭8 live on the Australian television broadcast of Guinness World Records.