Question: Who introduced a system of musical notation used in the region referred to as "the powderkeg of Europe" in the 14th century?

Knowledge 1: Powder keg of Europe
The powder keg of Europe or Balkan powder keg was the Balkans in the early part of the 20th century preceding World War I. There were a number of overlapping claims to territories and spheres of influence between the major European powers such as the Russian Empire, the Austro - Hungarian Empire, the German Empire and, to a lesser degree, the Ottoman Empire, the United Kingdom and Kingdom of Italy. [SEP] Knowledge 2: Late Middle Ages
The main representatives of the new style, often referred to as ars nova as opposed to the ars antiqua, were the composers Philippe de Vitry and Guillaume de Machaut. In Italy, where the Provençal troubadours had also found refuge, the corresponding period goes under the name of trecento, and the leading composers were Giovanni da Cascia, Jacopo da Bologna and Francesco Landini. Prominent reformer of Orthodox Church music from the first half of 14th century was John Kukuzelis; he also introduced a system of notation widely used in the Balkans in the following centuries.
Knowledge 1: Powder keg of Europe
The powder keg of Europe or Balkan powder keg was the Balkans in the early part of the 20th century preceding World War I. There were a number of overlapping claims to territories and spheres of influence between the major European powers such as the Russian Empire, the Austro - Hungarian Empire, the German Empire and, to a lesser degree, the Ottoman Empire, the United Kingdom and Kingdom of Italy. [SEP] Knowledge 2: Classical music
It is in this time that the notation of music on a staff and other elements of musical notation began to take shape. This invention made possible the separation of the composition of a piece of music from its transmission; without written music, transmission was oral, and subject to change every time it was transmitted. With a musical score, a work of music could be performed without the composer's presence. The invention of the movable-type printing press in the 15th century had far-reaching consequences on the preservation and transmission of music.
Knowledge 1: Powder keg of Europe
The powder keg of Europe or Balkan powder keg was the Balkans in the early part of the 20th century preceding World War I. There were a number of overlapping claims to territories and spheres of influence between the major European powers such as the Russian Empire, the Austro - Hungarian Empire, the German Empire and, to a lesser degree, the Ottoman Empire, the United Kingdom and Kingdom of Italy. [SEP] Knowledge 2: Hampartsoum Limondjian
Using his own system, Hampartsoum Limondjian transcribed most of 18th century Turkish music compositions in a collection of six books, which he presented to Selim III. Only two of the originals survive to date and are preserved at the Istanbul Municipal Conservatory Library. As the dominant notation for Turkish and Armenian music, the Hamparsum notation was instrumental in the transcription and survival of thousands of pieces of music, and was surpassed only in modern times in its use for Turkish classical music. The notation system is still in use by the Armenian Apostolic Church.

Answer: John Kukuzelis