In an attempt at reconstruction of historical events, as well as synthesis of the history of culture, the researcher needs documents created by the persons who participated in creation of said history. Primary sources such as diaries, memoirs and correspondence can clearly contribute to the understanding of the past and facilitate the interpretation of political and social events. Those sources are inevitably marked by the Zeitgeist of the time they were created; the time in which a contemporary researcher was not present, and their content is related to the then social, political and economic environment. Such documents are undoubtedly a rich source of information not only to historians but also to scholars in social sciences and humanities. Historians agree on the fact that letters are a valuable source for studying various aspects of society – they are a source for reconstruction of the social dimension of the history. What is more, their value as a source lies not only in what they include, but also in what they omit. Letters are not merely a reflection of social reality, but construct certain versions of that reality. Insight into one’s letters allows access to the author’s intimacy, thoughts, understandings, and emotions; the letters reflect author’s understanding of oneself and ideologies he believed into, bringing not only information about the time in which they were created, as well as about the readers of those letters themselves. Thus, Kuhač's letters are an authentic source useful for researching not only his personality but also the history of musicology. Correspondence, along with intimate comments, gives information on the methodology of early musicological and ethnomusicological research and depicts in great detail the situation at that time, i.e. the earliest stages of the development of musicology as a scientific discipline. During the 19th century significant political, social and cultural changes resulted with the interest for the "national" in music, as an aftereffect of political and cultural circumstances. Therefore, a need for preservation of the folk music heritage arose – Franjo Ksaver Kuhač was the first person who devoted his life to collecting folk music heritage in Croatian lands. His research opus was indispensable for the development of disciplines such as musicology, ethnomusicology and musical historiography in Croatia. Growing up during the National Revival and Revolution, the influential ideological enthusiasm of the Illyrian movement had a strong impact on his future ideas and prompted him to choose a Slavic cultural path. Building his cultural identity not on ethnicity but on cultural ideas, Kuhač was a passionate promoter of the Croatian National Revival, yearning to support the process of development and emancipation of South Slavic culture. With his work Kuhač above else attempted to corroborate the continuity of Slavic (Croatian) music history in the context of European music history, which would lead to constitution of Croatian cultural consciousness. His wide spectrum of scientific activity included researching, collecting, writing down and publishing traditional music and instruments of Southern Slavs, researching and writing history of music (mostly national), pedagogical work, endeavours in various types of activities (he was a music critic, authored music lexicons and dictionaries), as well as fieldwork and traveling. What is more, Kuhač preserved copies and concepts of his sent letters in order to keep track of everything he had written to his professional and private contacts and to leave material which could be used for writing his biography. This thesis researched ca. 3300 letters, written in Gothic and Latin script between years 1860 and 1911, which are a valuable source of information on cultural, political and musical events, as well as on Kuhač's life, work and activities. They are testimonies of the Zeitgeist and of the extremely rich network of prominent Croatian and foreign politicians, artists and pillars of cultural life. Kuhač was very much aware of the importance of networking, which in many ways facilitated his penetration into scientific and cultural circles. For years, he diligently established and maintained the professional and social contacts he desperately needed to collect folk songs and instruments, conduct his research, write scholarly articles, and disseminate the results of his work. In over half a century of active correspondence (1860–1911), Kuhač sent letters to over a thousand different addressees, including people in the highest and most powerful positions, such as Emperor Franz Josef I of Austria and Serbian Queen Natalia; eminent professors and intellectuals such as Eduard Hanslick and Istvan Bartalus, reputable Russian music publisher Pyotr Ivanovich Jürgenson, as well as numerous teachers and pastors who helped him with collecting of the national heritage. His correspondents lived in various countries (mostly in Central and Eastern Europe) and the length of the letters varies: some letters were written in the form of short messages and reminders, while longer ones deal in detail with certain topics, events and phenomena. After making summaries of all the letters, they were interpreted and contextualized according to their content and addressees. This thesis focuses on the addressees and the thematic content of the preserved letters which are classified according to seven thematic categories (collection of folk music heritage, presentation of Kuhač’s work and ideas on national music of (southern) Slavs, pleas for patronage, support and recommendations, arrangements with publishers and bookstores, procurement and resale of instruments, organization of music life, as well as cultural politics, socio-economic circumstances and Kuhač's relations with contemporaries). Furthermore, types of addressees were presented according to their occupation, social status and connections relevant for Kuhač and his work. Systematization of these topics and analysis of case studies brought a lot of new information about the birth of musicology as a scientific discipline in Croatia, Kuhač's research processes (his primary source of information was often unverified oral tradition) and the literature he consulted during his research on South Slavic music (and preparing his comparative studies about music historiography). Letters are a testimony of a direct (and often detrimental) influence of political and cultural circumstances on the work of artists and scientists. Moreover, it is a testimony of the phenomena of musical life and the general state of the Croatian political and cultural environment in the second half of the long 19th century. Additionally, the results of the analysis of the correspondence called into question previous perception of Kuhač as a modest and selfless person who, alone, neglected by the institutions and contemporaries, laid the foundations of Croatian musicology. His diligence and dedication to research is undisputed, however, he was in big part responsible was his unfavourable economic position. From the letters it is clear that Kuhač did not have a permanent employment for most of his life due to his pride, vanity and conflicting nature – unwilling to compromise, he in a way condemned himself to a lifelong struggle for existence. Also, it can be concluded that some of the Kuhač’s pleads for financial help and were not granted because, given the circumstances, Kuhač insisted on some unrealistic demands. Some of the topics (such as Kuhač's arrangements with publishers regarding the publication of his compositions) were written about for the first time, while certain topics (such as Kuhač's pleads to the Parliament, Government, institutions and dignitaries) have already been researched to some extent, however, this research has broadened the existing knowledge. Additionally, the dates and statements documented in the correspondence lead to the conclusion that certain “facts” concerning Kuhač's fieldwork, are, in fact, incorrect - such as the journey he allegedly undertook to Bulgaria and Macedonia in the summer of 1868. From the correspondence it is clear that time-wise, he could not have undertaken it, and that he did not undertake it in the future years. What is more, letters such as those addressed to Serbian composer Josif Šlezinger, in which Kuhač asked about Bulgarian songs and songbooks in order to finish his collection South-Slavic Folk Songs, further confirm the hypothesis. Correspondence also proved to be a valuable source for following all phases of Kuhač's professional advancement, from his attempt to present himself to the public as a South Slavic composer to his affirmation in the new field of musicology. Analysing written inquiries Kuhač sent to domestic and foreign publishers and bookstores and various scholars and music historians, one learns about his research processes. Such letters also confirm that he was relatively well acquainted with the existing older and newer literature, although it is unusual that none of the letters commenting on his ethnographic research mentions the works of Johann Gottfried Herder, who was an important figure in awakening Slavic national awareness and who introduced the term and idea of a folk song. Not to mention, the correspondence sheds light on Kuhač's dubious biographical data, such as Kuhač's untruthful statement that he studied piano with Franz Liszt in Weimar in 1857, which was later taken as undeniable truth by some authors. Primarily, reading all of Kuhač's correspondence, it can be taken as fact that Kuhač was by no means a modest and unpretentious person who would choose to leave out that he was Liszt's student, a feat he omitted in the content of many applications in which he represented himself, his education and work. Additional doubt is caused by the fact that he does not mention this information in the letter sent to Liszt himself when he asks him to support his collection South-Slavic Folk Songs, which would certainly increase his chances of receiving Liszt's support. In addition, letters have been preserved in which he untruthfully claims that Liszt was delighted with his work, since Liszt never replied to his letter. Being directed towards the problematics within the letters, types of addresses, Kuhač’s ways of communications, his opinions about culture and his own work, this research positions Kuhač’s ideas about national music and musical life within society in a broader context. A comprehensive picture of Kuhač, his work and legacy is outlined, including his interconnection with the musical, cultural, political and private affairs, along with various general and musical phenomena of the Croatian political-cultural existence.