Final answer:
The main forms of sacred choral music in the classical era were the Mass and the Motet, with composers focusing on structured melodies and harmonies while incorporating polyphonic textures from earlier periods into these forms.
Step-by-step explanation:
In the classical era, the main forms of sacred choral music were the Mass (a type of mass), and the Motet. Sacred music during this time was characterized by masses and motets, which were mainstays throughout the era. In contrast to later periods, such as the Romantic era, where composers like Brahms and Tchaikovsky pushed the boundaries of musical expression, classical era composers were more focused on the clear structure of music through melodies, harmonies, and adherence to established forms.
The medieval roots of this music can be traced back to monophonic Gregorian chant, which evolved into more complex polyphonic textures during the Ars nova. As time progressed, particularly during the Renaissance, there was a blending of secular forms such as the madrigal into sacred compositions, leading to a rich tapestry of forms and styles that expanded the repertoire of sacred music.