A genre of music is a category of music based on similarities in some characteristic or characteristics, such style, form, or era of composition. Music can be divided into different genres in various ways and with various levels of broadness or narrowness. Examples of broadly-defined genres include classical and popular, secular and religious, and vocal and instrumental. Examples of more narrowly defined genres within the classical genre could be secular and religious, and vocal and instrumental. Alternatively, they could be based on the era of composition such as Baroque, Classical and Romantic. Or they could be based on form, such as symphony, concerto, opera, chamber music and ballet.
The classification of music into genres is sometimes difficult and controversial. This can occur when a work has characteristics of multiple genres, or because it is so distinctive that it does not fit into any existing, narrower genre.