He has an ultimate 4 Octave vocal range. source is Michael Jackson's official Facebook page. Freddie Mercury and Michael Jackson were one of the only singers to have a 4 Octave vocal range in their time. As toi may know , high notes are a piece of cake for Michael. His normal chant pitch is already higher than 90% of the male singers today. When he hits a high note , like when he hit a G5 live in I'll Be There performance in 2001 , it's unmatchable. In "Elizebath I l’amour You" , he held a note for like 18 Seconds. His song "All In Your Name" , the who song is of high notes when Michael sings expect the words "Only god knows". He had a rare and great vocal range. Hope that helps.
