There are some voices that you hear, even in very early recordings, and you know that the artist is special. Sibiryakov is one of those artists. The breath control, the openness of the sound, the legato, and the consistent lack of squezzing the throat were remarkable, given the beautiful nature of his voice.
Generally speaking Russian singers in the 19th century received training from outside of Russia. Either the teachers went to Russia or the students went to the teachers in the West. There was a craze for western opera to a point where Russian audiences did not know who the Russian composers were. It seems that most of the influx of westerners and the sending of Russian artists abroad was paid for by the Russian Court.
The first great Russian composer to exploit native Russian music traditions into the realm of secular music was Mikhail Glinka (1804–1857), who composed the early Russian language operas Ivan Susanin and Ruslan and Lyudmila. They were neither the first operas in the Russian language nor the first by a Russian, but they gained fame for relying on distinctively Russian tunes and themes and being in the vernacular.