"Portamento, the practice of sliding between pitches, has traditionally been viewed as a tasteless Romantic excess in vocal performance. At the height of the Romantic era, however, singing treatises by Manuel Patricio Rodriguez Garcia, Alexis de Garaude, and Ferdinand Sieber openly discuss different types of portamento and when it is most appropriately used. Recordings by singers trained in the 19th c. such as Adelina Patti and Fernando de Lucia show it to be widely used and highly effective. Portamento was thus not a performer's unwelcome additon, but an integral part of performance practice." (Bellman, Jonathan)
"Portamento in Romantic Opera,"
Performance Practice Review:
2, Article 3.
Available at: http://scholarship.claremont.edu/ppr/vol5/iss2/3