My thesis "Sonata for clarinet and piano by Viktor Kalabis" is focused on one of concertantes pieces for clarinet and piano by Viktor Kalabis . The first part of the thesis deals with the life experience of the composer; the second part comprises an attempt to reflect the interpreter's perspective and expound interpretation issues. The author's experience with performing the sonata is described. The most difficult sections are explained and interpretation and practice options offered. The author's recording (2014 - J. Černohouzová, D. Wiesner) is compared with two other recordings (1970 - J. Štengl, Z. Zichová, 2013 - J.Hlaváč, I. Kahánek). The approaches of the interpreters and their performance style is analysed. The composer-interpreter relationship is discussed.

Viktor Kalabis (1923 - 2006) is one of the most significant Czech composers of 20th century. His piano works extent is exceptional among output of his contemporaries (two piano concertos with orchestra, three piano sonatas and six other compositions for piano solo). Most of his works are recorded and published. This dissertation concerns the personality of Viktor Kalabis, a characterization of his musical language and his approach to piano as a tool to express music. This instrument was closest to him and he often devoted to piano the most inner feelings. My aim was to explore his work from interpreter's point of view, the evolution of composer's musical language, the use of instrument's potential as well as new approaches and creation methods. I intended to engage the interest of pianist to V. Kalabis and remarkable qualities of his piano works. I have performed his music at important events (festival, Czech Philharmonic Orchestra concert season) and a concert dedicated to composer's anniversary was recorded by Czech Radio to be later released on CD. I used the musical analysis as the basic method. I observed the form, harmony, rhythm, usage of instrument's sound, timbre; in concertos also the role of the piano and of the orchestra. Kalabis wasn't a trendsetter of the avant-garde and he didn't adopt dodecaphonic technique, however he studied it and implemented some dodecaphonic principles. For some period he worked in neoclassicism and shortly neofolklorism styles. He built on traditional harmony, which he enriched with seconds and sevenths proceeding to bitonality and partially also to atonality. He uses both traditional and free forms. Innovation can be found above all in original sound, in creative grouping of instruments and in dramaturgical content of the piece. He laid stress on composition's revealability and listener-friendly character, without being pandering. He created original "non-romantic synthesis" musical language.