Divides text into syllables using the TeX hyphenation patterns from
slavonic/cu-tex, for marking melismatic chant text.
Paste lyrics, pick a rule set, copy the result.
Typographic applies the patterns exactly as TeX does when breaking lines. It deliberately refuses to break after a word-initial single-letter syllable, so и҆́же stays whole — right for typesetting, wrong for chant.
All boundaries drops those word-edge suppressions and shows every syllable boundary the patterns know: и҆́_же.
Singing additionally moves a single consonant between two vowels into the following syllable, so раз_ꙋ́мныхъ becomes ра_зꙋ́м_ныхъ. The patterns encode morphological boundaries (the prefix раз-); singers divide on open syllables. Use this one for melisma marking, and check the output — the two conventions genuinely disagree, and the patterns are the authority on morphology, not on how a given melody is underlaid.
One exception in Singing: a consonant carrying a yerok stays put, because the yerok stands for an elided ъ and closes the syllable — пред̾_ꙋ_го_то_ва, not пре_д̾ꙋ_го_то_ва.
Breaks are never placed before a combining mark, so accents, breathings and titla stay with their letter. Punctuation, spacing and line breaks pass through untouched.