Opera has now and then been observed through the lens of its composers and their works, but this has usually been subordinate – for the interested public at least – to its study through the lens of the singers them selves. It is the canary fancier who forms the opera fan, and it is he who now populates the e-waves with chitchat, gossip, and eccentric theories.

And it has been the singers themselves who have fueled opera for most if not all of its 400-year existence.

Their extraordinary abilities – and their excesses – have been the hope and despair of countless composers, not least Handel, Verdi, and Wagner. Their stories, real or imagined, and the anecdotes about them will always make good operatic copy (much better than a study of the key relationships in Mozart’s “Le Nozze di Figaro”), and are well worth periodic revisits. In “Angels and Monsters: Male and Female Sopranos in the Story of Opera” (Yale University Press, 310 pages, $30), Richard Somerset-Ward has chosen to take us through the history of the soprano (and, in part, the mezzo) voice from opera’s beginning to the early 20th century.

Mr. Somerset-Ward provides a pleasant and rewarding journey (one that is also considered in Rupert Christiansen’s 1984 “Prima Donna,” which carries the story down to our times). He is especially valuable in his discussion of the castrato voice, and the exemplars of that singing (e.g. Farinelli). The recent popularity of Handel operas has brought back their kind of vocalism, but we shall never again hear exactly what these singers sounded like – today’s growing breed of countertenors (both alto and soprano) are but pale imitations of the real thing.

The latter chapters of the book discuss the singers who sang the music of the two 19th-century operatic giants, Verdi and Wagner, and the book ends with the careers of Nellie Melba, Emma Eames, and Mary Garden. Mr. Somerset-Ward details how the bel canto singing tradition of the early 19th century became more and more corrupted by the demands of Verdi for more drama in the voice and by Wagner for a larger orchestra and more musicodramatic weight placed on singing. He is of course correct about this, though the later 20th century has seen at least a partial revival of the bel canto tradition.

As with Mr. Christiansen’s book, there is a loss when the male side (or non-castrated male) is not similarly elaborated and discussed. Yes, this is asking for a book the author did not intend to write. But a full understanding of what happened to the voice between 1800 and, say, 1930, requires its being considered in terms of both sexes. These female angels and monsters may have made for better copy in the tabloids, but to tell only about some of the parts is to only partly tell the history of the voice in opera – which is also what the author is writing.

Nonetheless, what Mr. Somerset-Ward does tell us is good and enlightening reading.