Despite the fact that Bohemian capital city Prague was always considered as the heart of Europe, the Czech lands played a rather receptive role in the field of music in the Middle Ages. The conservatism of this environment was reflected in the repertoire, which by that time had long since fallen out of fashion in Western Europe, but was still being composed and performed in Prague. Thanks to this, however, we have preserved absolute gems in domestic sources, which sound like an early Aquitanian polyphony (organum), with a touch of later polyphonic style. The most beautiful pieces of this late organum are found in the sources for Advent and Christmas period.