Abstract: This article examines a unique document: a singing manuscript by to the famous Old Believer of the Fedoseevsky (Bespopovsty) movement, the typographer and educator Luka Arefyevich Grebnev (1867 - 1932). The author comes to the conclusion that the surviving draft is a draft edition of liturgical chants. The author examines in detail how Grebnev edited liturgical texts and melodies, what was his intention, and why Luka Arefievich addressed at all the issue of liturgical singing. The author also considers Grebnev's role as the organizer of the church choir at the chapel in the village of Staraya Tushka in the Malmyzhsky uyezd of the Vyatka governorate. A vast array of various sources was used for this research: singing books, documents of epistolary nature and diaries, materials from Old Believer cathedrals, the investigation file on the deprivation of the Grebnev family of electoral rights, and others. The decoding of the musical notes on the hooks of the manuscript by L. A. Grebnev was made using several singing alphabets (preference was given to the data from the Alphabet uncovered by archaeographers in Vyatka). Based on the decoding, the author conducted a musicological analysis of the edits of the liturgical chants proposed in the manuscript. The other sources allowed to restore the historical and biographical context of the manuscript. The article addresses the practically unstudied side of Luka Arefyevich Grebnev's activity in reforming liturgical singing. The author comes to the conclusion that his edits were aimed first of all at correcting the text of the hymns - the abolition of archaisms. A similar idea was actively discussed at councils of Old Believers at the turn of the 19th - 20th centuries. Grebnev's merit lies in that he intended to submit for discussion at the forthcoming All-Russian Fedoseyevsky council his finalized edition of liturgical chants. This is why the document itself is a unique source in the history of Orthodox church music. The analysis of the manuscript has made it possible to conclude that Grebnev acted within the framework of traditional for Old Russian church and singing art methods, sparing compared to the original chants. At the same time, the correction of liturgical chants in itself meant a cardinal revolution in the church life of the Old Believers.