The term "bel canto" refers to the Italian-originated vocal style that prevailed throughout most of Europe during the 18th century and lingered in a less elaborate but still dominant form until around 1840. The hallmarks of the bel canto style were:

Operas and oratorios highly conducive to this method of singing were composed by George Frideric Handel (1685–1759) and his contemporaries during the Baroque period. They contained da capo arias which were designed to provide solo singers with plentiful opportunities to display their technical skill and demonstrate their ability to improvise on the spot by embellishing the written score in a (hopefully) tasteful and illuminating manner. Da capo arias featured extensive and elaborate ornamentation, demanding much from the vocalist in the way of fluent runs, trills, turns (gruppetti), mordents, morendi, roulades, staccato passages, appoggiaturas,acciaccaturas, marcato notes, messa di voce effects, rapid scales, wide leaps spanning two octaves or more and brilliantcadenzas. In short: what is commonly referred to by opera-goers as coloratura.

Two famous 18th-century teachers of coloratura vocalism were Antonio Bernacchi (1685–1756) and Nicola Porpora (1686–1768), but numerous others existed. A large proportion of these teachers were castrati. Singer/author John Potter declares in his book Tenor: History of a Voice (Yale University Press, 2009, p. 31) that: "For much of the 18th century castrati defined the art of singing; it was the loss of their irrecoverable skills that in time created the myth of bel canto, a way of singing and conceptualising singing that was entirely different from anything that the world had heard before or would hear again."

In a narrower application, the term "bel canto" is sometimes attached exclusively to Italian opera of the time of Gioachino Rossini (1792–1868), Vincenzo Bellini (1801–1835) and Gaetano Donizetti (1797–1848). These three composers wrote bravura works for the stage during what musicologists call the bel canto era, which lasted approximately from 1805 to 1840. The bel canto era preserved many of the Baroque's musical values, although such characteristic forms as opera seria and the da capo aria did not survive the passing of the 18th century. Changing tastes and social standards also killed off the operatic castrato voice and ensured the concomitant rise to singing supremacy of theprima donna soprano and the virtuoso tenor. (The last important opera role for a castrato was written in 1824 by Giacomo Meyerbeer [1791-1864].)

Actually, the phrase "bel canto" did not enter common usage until the middle of the 19th century, when it was set in opposition to the development of a weightier, more powerful style of speech-inflected singing associated with German opera and, above all, Richard Wagner's revolutionary music dramas. Wagner (1813–1883) decried the Italian singing model, alleging that it was concerned merely with "whether that G or A will come out roundly". He advocated a new, Germanic school of singing which would draw "the spiritually energetic and profoundly passionate into the orbit of its matchless Expression".

Interestingly enough, French musicians and composers never embraced the more florid extremes of the 18th-century Italian bel canto style. They disliked the castrato voice and because they placed a premium on the clear enunciation of the texts of their vocal music, they objected to the sung word being obscured by excessive fioritura.

The popularity of the bel canto style as espoused by Rossini, Donizetti and Bellini faded in Italy during the mid-19th century. It was overtaken by a heavier, more ardent, less embroidered approach to singing that was necessary in order to perform the innovative works of Giuseppe Verdi (1813–1901) with maximum dramatic impact. Tenors, for instance, began to inflate their tone and deliver the high C (and even the high D) directly from the chest rather than resorting to a suave head voice/falsetto as they had done previously, sacrificing vocal agility in the process. Sopranos and baritones reacted in a similar fashion to their tenor colleagues when confronted with Verdi's drama-filled compositions. They subjected the mechanics of their voice production to greater pressures and cultivated the exciting upper part of their respective ranges at the expense of their mellow but less penetrant lower notes. Initially at least, the singing techniques of 19th-century contraltos and basses were less affected by the musical innovations of Verdi, which were built upon by his successors Amilcare Ponchielli (1834–1886) and Arrigo Boito (1842–1918).

One reason for the eclipse of the old Italian singing model was the growing influence within the music world of bel canto's detractors, who considered it to be outmoded and condemned it as vocalization devoid of content. To others, however, bel canto became the vanished art of elegant, refined, sweet-toned musical utterance. Rossini lamented in a conversation that took place in Paris in 1858 that: "Alas for us, we have lost our bel canto". Similarly, the so-called German style was as derided as much as it was heralded. In the introduction to a collection of songs by Italian masters published in 1887 in Berlin under the title Il bel canto, Franz Sieber wrote: "In our time, when the most offensive shrieking under the extenuating device of 'dramatic singing' has spread everywhere, when the ignorant masses appear much more interested in how loud rather than how beautiful the singing is, a collection of songs will perhaps be welcome which – as the title purports – may assist in restoring bel canto to its rightful place."

Musicologists occasionally apply the label bel canto technique to the arsenal of virtuosic vocal accomplishments and concepts imparted by singing teachers to their students during the late 18th century and the early 19th century. Many of these teachers were castrati.

"All [their] pedagogical works follow the same structure, beginning with exercises on single notes and eventually progressing to scales and improvised embellishments," writes Potter on p. 47 of his Tenor: History of a Voice. "The really creative ornamentation required for cadenzas, involving models and formulae that could generate newly improvised material, came towards the end of the process." (Today's pervasive idea that singers should refrain from improvising and always adhere strictly to the letter of a composer's published score is a comparatively recent phenomenon, promulgated during the first decades of the 20th century by dictatorial conductors such as Arturo Toscanini [1867-1957], who championed the dramatic operas of Verdi and Wagner and believed in keeping performers on a tight interpretive leash. See, for instance, Volume 1 of Michael Scott's survey The Record of Singing [Duckworth, London, 1977], pp. 135–136; also Potter, p. 77.)

Potter notes, however, that as the 19th century unfurled, "The general tendency ... was for singers not to have been taught by castrati (there were few of them left) and for serious study to start later, often at one of the new conservatories rather than with a private teacher. The traditional techniques and pedagogy were still acknowledged, but the teaching was generally in the hands of tenors and baritones who were by then at least once removed from the tradition itself."

Early 19th-century teachers described the voice as being made up of three registers. The chest register was the lowest of the three and the head register the highest, with the passaggio in between. These registers needed to be smoothly blended and fully equalized before a trainee singer could acquire total command of his or her natural instrument, and the surest way to achieve this outcome was for the trainee to practise vocal exercises assiduously. Bel canto-era teachers were great believers in the benefits of vocalise and solfeggio. They strove to strengthen the respiratory muscles of their pupils and equip them with such time-honoured vocal attributes as "purity of tone, perfection of legato, phrasing informed by eloquent portamento, and exquisitely turned ornaments", to quote from the introduction to Volume 2 of Scott's The Record of Singing (Duckworth, London, 1979).

Major refinements occurred to the existing system of voice classification during the 19th century as the international operatic repertoire diversified, split into distinctive nationalist schools and expanded in size. Whole new categories of singers such as mezzo-soprano and Wagnerian bass-baritone arose towards the end of the 19th century, as did such new sub-categories as lyric coloratura soprano, dramatic soprano and spinto soprano, and various grades of tenor, stretching from lyric through spinto to heroic. These classificatory changes have had a lasting effect on the way singing teachers designate voices and the way in which opera house managements cast their productions.

It would be wrong, however, to think that there was across-the-board uniformity among 19th-century bel canto adherents when it came to passing on their knowledge and instructing students. Each of them had their own training regimes and pet notions; but, fundamentally, they all subscribed to the same set of bel canto precepts, and the exercises that they devised in order to enhance their students' breath support, dexterity, range and technical control remain valuable and, indeed, are still employed by some teachers.

Manuel García (1805–1906), author of the influential treatise L'Art du Chant, was the most prominent of the group of pedagogues that perpetuated bel-canto principles in their teachings and writings during the second half of the 19th century. His like-minded younger sister, Pauline Viardot (1821–1910), was also an important teacher of voice, as were Viardot's contemporaries Mathilde Marchesi, Camille Everardi, Julius Stockhausen, Carlo Pedrotti, Venceslao Persichini, Giovanni Sbriglia, Melchiorre Vidal andFrancesco Lamperti (together with Francesco's son Giovanni Battista Lamperti). The voices of a number of their former students can be heard on acoustic recordings made in the first two decades of the 20th century and re-issued since on LP and CD. Some examples on disc of historically and artistically significant 19th-century singers whose bel canto-infused vocal styles and techniques pre-date the "Bayreuth bark" and the dramatic excesses of verismo opera are:

Sir Charles Santley (born 1834), Gustav Walter (born 1834), Adelina Patti (born 1843), Marianne Brandt (born 1842), Lilli Lehmann (born 1848), Jean Lassalle (born 1847),Victor Maurel (born 1848), Marcella Sembrich (born 1858), Lillian Nordica (born 1857), Emma Calvé (born 1858), Nellie Melba (born 1861), Francesco Tamagno (born 1850),Francesco Marconi (born 1853), Léon Escalais (born 1859), Mattia Battistini (born 1856), Mario Ancona (born 1860), Pol Plançon (born 1851), and Antonio Magini-Coletti and Francesco Navarini (both born 1855).