The master's thesis characterises the Russian sacred musical expression from the 10th to the 17th century and analyses the ways in which it has appeared since then. In the thesis, I will evaluate how music conveys its message, what role it plays in rituals and how it influences a person's development and perception. One of my focuses is Russian musical expression after the conversion to Christianity. I will also consider the elements, which the new musical expression has preserved from the Pagan era and the ones it has borrowed from Byzantine or Greek music culture. Furthermore, I will characterise the most important form of a chant and its variations, as well as present the transcription of music during that period, question the role of a creator of worship service pieces and illustrate the primary purpose of music in worship service. I will concentrate on Russian sacred music features, specifically, the relationship between instrumental and vocal music, the role of singers in worship service, oktavists and the space or acoustics of an orthodox church. The thesis concludes by presenting the echo of the discussed music in Slovenia.