What characterises medieval polyphony and song? Who composed this music, sang it, and wrote it down? Where and when did the different genres originate, and under what circumstances were they created and performed? This book gives a comprehensive introduction to the rich variety of polyphonic practices and song traditions during the Middle Ages. It explores song from across Europe, in Latin and vernacular languages (precursors to modern Dutch, English, French, German, Italian, Portuguese and Spanish); and polyphony from early improvised organum to rhythmically and harmonically complex late medieval motets. Each chapter focuses on a particular geographical location, setting out the specific local contexts of the music created there. Guiding the reader through the musical techniques of melody, harmony, rhythm, and notation that distinguish the different genres of polyphony and song, the authors also consider the factors that make modern performances of this music sound so different from one another.