This is a troparion for St Ivan Rilski (St John of Rila). It is also an example of the Eastern Orthodox chants, which are way more complex and elaborate than the western ones. A simple example illustrating that difference is that for every single western musical note (the notes used today and that were used by the classics) there are four eastern notes. In other words the Eastern Orthodox chanters were able to distinguish and reproduce four different sub-notes to each note so to speak.
