LONDON — The vast collection of Russian art belonging to the recently deceased cellist Mstislav Rostropovich and his wife, the soprano Galina Vishnevskaya, will go on sale next week at Sotheby’s in London. There are more than 450 lots, estimated at a value between $26 million and $40 million — the biggest single collector sale of Russian art to date. And the timing is right: Prices have been driven by an exploding Russian art market, which the director of Russian art at Sotheby’s London, Jo Vickery, says has quadrupled in the last five years.

Rostropovich and Ms. Vishnevskaya began collecting shortly after being exiled from Russia in 1974 for disagreeing with the country’s restrictions on artistic freedom. Offenses included sheltering banned novelist Alexander Solzhenitsyn and writing an open letter of dissent to the government in 1970. Yet it was in Russia that the pair became stars. In 1945, at age 18, Rostropovich won the gold medal in the Soviet Union’s first competition for young musicians and became a celebrity overnight. As a darling of the USSR, he toured every major city in Eastern Europe and won — among many awards — the prestigious Lenin Prize in 1963. National composers, including Prokofiev, Shostakovich, and Khachaturian began to write music specifically for him. In 1955, he married Ms. Vishnevskaya, who sang for the Bolshoi Opera.

Their experience of their homeland fueled a desire to collect and, perhaps, to try to restore an ideal of pre-communist Russia. The result is an extraordinary collection of Russian 18th-, 19th-, and 20th-century art and decorative pieces. The professor of Russian history at Cambridge University, Simon Franklin, said: “What drives the post-Soviet market is not so much to do with Imperial Russia itself but with what people think it might have been. It’s nostalgia, a need to reconnect with pre-Soviet Russia.”

Whatever the exact reason, the couple crammed their houses in Paris and London with Imperialist portraiture, expressionist Revolutionary painting and a dazzling array of porcelain and enamels in an effort to make what Ms. Vishnevskaya called “a Russian house.” Among the latter are a prized gold-mounted 1768 snuff box (estimated at between $305,000 and $407,000) and a variety of 18th-century walrus bone mirrors, mini-caskets, and other boxes.

Possibly the greatest and one of the latest pieces in the sale is the Expressionist work “Faces of Russia,” painted in 1921 by Boris Dmitrievich Grigoriev (estimated at between $3 million and $4 million) on the eve of his move to Paris from Berlin. It focuses on the faces of country people, disoriented and morose, as they suffer through the upheaval of the revolution. Predictably, devoted communists such as Alexei Tolstoy were not enamored of the work, calling it a “thoughtless expression” of “stony obsolete ghosts.” The critic Claire Sheridan has called it “the greatest work to come out of Russia since the Revolution.”

Very popular in Russia but rarely seen at auction is the work of Karl Pavlovich Briullov (1799–1852), a meticulous copier of fabric and finery. In this collection, there is a luminous portrait of the beloved patroness and humanitarian Princess Aurora Demidova (estimated at between $1,630,000 and $2,440,000). Rare, too, at auction are paintings by Valentin Serov (1865–1911). This sale includes a portrait of Prince Felix Yusupov, the father of the man who killed Rasputin (estimated at between $1.6 million and $2,4 million).

Much attention has been given to the diverse 21 paintings by Ilya Efimovich Repin (1844–1930), one of Russia’s greatest figurative artists. Ms. Vickery calls it the largest collection she has ever come across. They range from humble sketches of smiling, bearded Cossacks (estimated at between $8,200 and $12,200) to a lively high-society scene called “The Ballroom,” expected to go for up to $407,000, and several haunting portraits of women in various states of undress and distress. “Bolsheviks,” a poignant, unflattering picture of grasping peasants (around 1930), has never before been seen in public.

The couple’s Paris apartment was crammed with Imperial portraiture — tsars and tsarinas everywhere. A grandiose painting of Catherine the Great completed in 1793 by the serf Ivan Pustynin is expected to sell for as much as $305,000.

And there is a large amount of theatrical art, in keeping with the profession of its collectors. Most glorious is a set design for “Sleeping Beauty” (estimated at between $30,000 and $40,700) by the Franco-Russian artist Benois, a key figure in the Ballet Russe.

“What is extraordinary about this collection is the revelatory aspect of it; this private side of Rostropovich and Vishnevskaya,” Ms. Vickery said. “In all the biographies, there is little or no mention of the collection and certainly nobody could have anticipated its sheer enormity.” Sotheby’s expects mainly Russian buyers at the sale and — as Rostropovich and Ms. Vishnevskaya wished — much of it will likely return to Russia.

But Rostropovich was loved the world over and a broader audience is interested in this sale. “Until now, the West has been very aware of other Russian art forms, such as music and ballet, because it travels,” Ms. Vickery said. “The decorative art and paintings tends to stay in Russia, in museums. But this sale should show the world a window onto Russian art.”