Up to around 1300, most musical compositions were monophonic, i.e., composed with a single melody line, for example for a single voice, unaccompanied or accompanied at the same pitch. The ballate in the Decameron, for example, are clearly monophonic, in that they are sung by a single character. As the ballata genre developed, other voices were added, and the polyphonic ballata enjoyed great popularity in the later Trecento.
Polyphony began to develop in sacred music during the ninth to thirteenth centuries. The main melodic line of the chant began to be embellished by the simultaneous sounding of additional harmonies, thus altering the sound of Western music forever.