Vocal Type: Soprano
Vocal Range: 3 Octaves F3-E6 (though the E6's vibrato touches an F6, so will count as 3 octaves)
Whistle Register: No
Vocal Pluses:Callas's voice was noted for its three distinct registers: Her low or chest register was extremely dark and almost baritonal in power, and she used this part of her voice for dramatic effect, often going into this register much higher on the scale than most sopranos. Her middle register had a peculiar and highly personal sound—"part oboe, part clarinet", as Claudia Cassidy described it—and was noted for its veiled or "bottled" sound, as if she were singing into a jug. Legge adds, "Even in the most difficult fioriture there were no musical or technical difficulties in this part of the voice which she could not execute with astonishing, unostentatious ease. Her chromatic runs, particularly downwards, were beautifully smooth and staccatos almost unfailingly accurate, even in the trickiest intervals. There is hardly a bar in the whole range of nineteenth century music for high soprano that seriously tested her powers."
Vocal Negatives: Rodolfo Celletti states, "In certain areas of her range her voice also possessed a guttural quality. This would occur in the most delicate and troublesome areas of a soprano's voice—for instance where the lower and middle registers merge, between G and A. I would go so far as to say that here her voice had such resonances as to make one think at times of a ventriloquist. . .or else the voice could sound as though it were resonating in a rubber tube. There was another troublesome spot. . . between the middle and upper registers. Here, too, around the treble F and G, there was often something in the sound itself which was not quite right, as though the voice were not functioning properly."
Note:I am in no position to be a judging a voice like this- you need college degrees and schooling to do that- so I pinched the positives and negatives from Wikipdiea. I am forever in your debt! Read the article
here, its fascinating stuff.