The Codex Speciálnik (c. 1485-1500), an important European music manuscript of its time, contains about 200 pieces of fifteenth-century polyphony. Its repertory includes contemporary music written by leading composers of the second half of the fifteenth century (from Pullois to early works of Josquin and his contemporaries), as well as pieces of Central European origin. A group of compositions called 'sociorum' seems to represent a specific local repertory written in low register (for male voices only) and can be found exclusively in the Codex Speciálnik (except for two compositions with concordances in sixteenth-century Bohemian and German sources). The parts of mass ordinary 'sociorum' can be divided into two groups: 1) compositions with an identified model and 2) free compositions. The incomplete cycle No. 1 is built on the chanson 'Corps digne-Dieu quel marriage' by Busnois and a song-like Bohemian ,Patrem'; the cantus firmus of the pair No. 47 paraphrases the antiphon 'O admirabile commercium' and the pair No. 197 is built on chants 'Credo I' and 'Sanctus I' organically incorporated into the polyphonic structure. The form of the free-composition pieces is based on the structure of their texts, usually following its short phrases. The compositional style of the 'sociorum' pieces can be characterized by the prevailing 'major' tonality, frequent use of cadences, short imitations, sequences, ostinati and homophony. The repertory of the Codex Speciálnik is witness to the knowledge of imported international repertory in one of the Bohemian cultural centres of the time (possibly Prague) at the end of the fifteenth century. It also reflects the ways in which older musical traditions were cultivated and the local contemporary compositional style developed, a style which it would be useful to study in the context of similar compositions of Central European origin.