What was an unaccompanied secular vocal song in the Renaissance called?

During the Renaissance, the madrigal emerged as a popular form of unaccompanied secular vocal music. Typically written for multiple voices, madrigals were characterized by their expressive lyrics and intricate polyphonic textures. They often explored themes of love, nature, and human emotion, making them a favorite among both composers and audiences of the time.

The madrigal's structure allowed for creative vocal interplay, where each voice could weave in and out, creating a rich tapestry of sound. Composers such as Thomas Morley and Claudio Monteverdi significantly contributed to the development of this genre, making it a defining element of Renaissance music.

In contrast, other types of music mentioned do not fit the specific description of an unaccompanied secular vocal song. The galliard, for instance, is a dance form rather than a vocal piece. The chanson, while also a vocal form, is typically associated with French music and can involve instrumental accompaniment as well. Folk songs generally refer to traditional music passed down orally, which does not align with the more formalized and composed nature of madrigals. Thus, the madrigal distinctly fulfills the criteria established in the question as the unaccompanied secular vocal song of the Renaissance.