Born on December 13, 1877, in the village of Monastyrk in the Bratslav district of Podolia province to a rural priest's family. He spent his early years in the village of Shershni in the Tyvrov volost of the Vinnytsia district. Leontovich received his initial musical education from his father, who played the cello, violin, guitar, and for some time conducted a choir of seminarians. In 1892, he entered the Podolian Spiritual Seminary in Kamianets-Podilskyi, where he studied music theory and choral singing, mastered the violin, piano, and some wind instruments, and began arranging folk melodies for the collection 'Bohohlasnyk,' inspired by the arrangements of Mykola Lysenko. In the autumn of 1904, he left Podolia and moved to Donbas, where he became a singing and music teacher at the railway school in Hryshyne (now the city of Pokrovsk). He worked there from 1904 to 1908 and organized a workers' choir that performed at rallies. From 1909, Leontovich studied under the renowned music theorist Boleslav Yavorsky, whom he periodically visited in Moscow and Kyiv. During this period, he created numerous choral arrangements, including the famous 'Shchedryk,' as well as 'Mala mati odnu dochku,' 'Dudaryk,' 'Oy, zayshla zorya,' and others. In Tulchyn, he met composer Kyrylo Stetsenko. In 1916, together with the choir of Kyiv University, he performed his arrangement of 'Shchedryk,' which brought him great success with the Kyiv audience.