It seems that the composers from Monteverdi on for two and a half to three centuries composed their music in recognition of what the human voice could do and express as a whole. Bel canto, as an ideal, not only satisfied an aesthetic, but also meant ‘skilful’, ‘expressive’ and, I believe, healthy singing.
Vocal music of the 20th century (with some notable exceptions) became vocally brutalising, divisive and effortful. The singing world ignored E. F. Schumacher’s maxim ‘small is beautiful’. Small, for more than half a century, has been anathema, and uneconomical besides. The irony is that the ‘big is beautiful’ idea has spawned generations of less than beautiful, strained singing, while producing pitifully few voices able to sing the music of Verdi or Wagner.
In the same period of time much of the singing of so-called Early Music has gone to the other extreme of passionless propriety, often arising from or creating limited vocal resources and invariably based in ‘authentic’ artifice. In between we have an overly ‘intellectual’ lieder tradition, based in part I suspect on poor imitation of, for example, the superb young Fischer-Dieskau.
Harrison, Peter T. The Human Nature of the Singing Voice: Exploring a sound basis for Teaching and Learning. Dunedin Academic Press Ltd. 2016.