The original title of this graphic is The Vocal Ranges of the World's Greatest Singers. If you are confused as to why Axl Rose is on top of the chart over voices like Freddie Mercury or why the hell Lana del Rey and Lady Gaga are in this list, don't worry, it all has an explanation.
The explanation is that these are not the greatest singers in the world. Some of them are, of course. But others are not because having a wide vocal range doesn't have a lot of importance when it comes to be a truly amazing singer.
The textbook definition of vocal range is "the measure of the breadth of pitches that a human voice can phonate." But wven while you can hit all those notes, there are many more factors that separate the Lana del Reys and Lady Gagas of this world from the actual greatest singers of all time.
First is the tessitura, which is "where the voice is most comfortable singing." While Axl Rose can hit more octaves than Freddie Mercury, that doesn't mean that Axl Rose is able to maintain those notes or hit them easily. Mercury, on the other hand, was known for his amazing flexibility.
But perhaps the most important thing is the sound of the voice — the timbre — what distinguishes a rich voice full of personality from the run-of-the-mill voice pop voices that populate the charts.
That's why most bands and singers today sound more or less the same, especially across each category. Example: Whiny folksy indie singers all sound the same. People like Freddie Mercury, David Bowie, Elvis Presley, Nina Simone, Aretha Franklin, Johnny Cash, Van Morrison, Marvin Gaye or Tom Waits — to name a few from the list — have a distinct personality that has little to do with their vocal range, even while their vocal ranges allow to do certain things. Cash may not be able to hit the high notes of Christina Aguilera but that raged voice was light years ahead in texture and personality.