Musicologist and music cognition scholar David Huron of The Ohio State University finds that operatic singing does indeed scientifically qualify as screaming:

When opera singers want to drive the emotion, they do something with their larynx that puts their voices into that 2,000- to 3,000-hertz range — approximating a human scream.

His newest book, Sweet Anticipation: Music and the Psychology of Expectation, came out in the spring. I’m off to find a copy.