Life and Monastic Service
According to the synaxarion, Leontius came to the Kiev Caves monastery while still young and received monastic tonsure there. Having become literate, and being endowed with a fine voice, he was appointed canonarch — the cantor responsible for leading the church singing.
The office of canonarch was a specialized liturgical role: the lead cantor or reader who ensured that the other readers chanted from the correct texts and in the proper tones, preserving the canonical order of the services through correct use of the Typicon, and performing particular musical duties such as intoning the verses of the prokeimenon. The canonarch thus functioned both as a musician and as a guardian of the liturgical order, a role distinct from that of a general cantor.
Leontius reposed at a young age. The tradition of the monastery relates that he was glorified by the Lord for his selfless ascetic labors with the gift of miracles.