Sophia Gladkaya, married name Kedrova (full name Sophia Nikolaevna Kedrova), was a Russian opera, drama and chamber singer with a lyric soprano voice, and a music teacher. She was born on 25 December 1874 in St. Petersburg, into the family of a general in the Russian army. She studied at the Catherine Institute, one of St. Petersburg's most privileged educational institutions, before undertaking vocal studies at the St. Petersburg Conservatory from 1893 to 1898 with Natalya Iretskaya and Oskar Palechek.
From 1898 to 1900, Gladkaya sang with Savva Mamontov's Moscow Private Russian Opera. On 22 October 1899 she created the role of Domna Saburova in the premiere of Nikolai Rimsky-Korsakov's The Tsar's Bride. A critic praised her Domna as a complete, lifelike and convincing character, marked by natural humor and demonstrating the flexibility of her talent.
In 1900 she made her Mariinsky Theatre debut as Marguerite in Gounod's Faust. Following the successful debut, she joined the company and served as a soloist at the St. Petersburg Mariinsky Theatre from 1900 to 1905. Alongside her operatic work, she appeared occasionally in dramatic productions in 1901–02 and gave concerts, including symphonic concerts and programs of the Circle of Russian Music Lovers. She also performed in concerts with her husband, Nikolai Kedrov.
Her concert repertoire included music by Glinka, Dargomyzhsky, Mussorgsky, Cui, Borodin, Balakirev, Anton Rubinstein, Arensky, Tchaikovsky, Rachmaninoff, Glazunov, Brahms, Wagner, Debussy and Richard Strauss. She was the first performer of several romances by César Cui. Among her notable appearances were the solo part in Mozart's Mass in C minor, given in Russia for the first time on 19 February 1905; Beethoven's Mass in C major; Schumann's oratorio Paradise and the Peri; Brahms's A German Requiem; and Rossini's Petite messe solennelle, which she also introduced in Russia.
Gladkaya created the roles of Vera Sheloga in Boyarynya Vera Sheloga, Grishka in the prologue to In 1812, Domna Saburova in The Tsar's Bride, and Urvazi in Urvazi, the Morning Star. Her other roles included Tatiana in Eugene Onegin, Volkhova in Sadko, Micaëla in Carmen, Marfa in The Tsar's Bride, Xenia in Boris Godunov, Cherubino in The Marriage of Figaro, Marguerite in Faust, Juliet in Roméo et Juliette, and Elsa in Lohengrin. She toured Odessa, Kyiv, Mykolaiv, Kazan, Kislovodsk and Paris, where she appeared in 1912; in 1916 she sang Donna Anna in The Stone Guest at the Mikhailovsky Theatre in Petrograd. Critics noted her small but pure, silvery-toned voice, acting ability, expressive phrasing and grace.
Beginning in 1903, Gladkaya taught at the St. Petersburg Conservatory, becoming a professor in 1913. She continued teaching there in 1903–18 and 1921–22. Her pupils included Raisa Gorskaya, Kira Dorlíac, Alexandra Kobzareva, Alexandra Kropivnitskaya and Vera Pavlovskaya.
In 1922, the Kedrov family moved first to Berlin and then, in 1928, settled in Paris. There, Gladkaya and her husband both taught at the Paris Conservatory, while Nikolai Kedrov re-established his male vocal ensemble, the Kedrov Quartet. Sophia Gladkaya died in France in 1965.