bourdon / burden [ˈbɜrd(ə)n]
bourdon – n. music – 1. a low-pitched stop in an organ or harmonium; 2. the lowest bell in a peal of bells; 3. the drone pipe of a bagpipe
burden – n. – 1. a task or weight carried particularly for a long time or journey; 2. something that is exacting, oppressive, or difficult to bear, onerous; 3. Naut. – the cargo capacity of a ship; the weight of a ship’s cargo; 4. a line of words recurring at the end of each verse of a song; chorus or refrain; 5. the theme of a speech, book, etc