SUMMARY
The decoding of Kogoj’s intriguing numerical labelling of chords in this discussion presents an important step ahead in understanding of Kogoj’s invention of so-called chord permutations. The use of those is confirmed and situated within an aesthetic and dramatic context of the opera Black Masks (based on a drama by L. Andreyev), where Classicism and Modernism are linked together into a harmonious whole. In this regard, it represents an innovative contribution to Slovenian opera at the beginning of the 20th century.