This dissertation explores how nuns of the Order of the Immaculate Conception (Conceptionists) became some of the most important contributors to the soundscape of seventeenth- and eighteenth-century Mexico City and Puebla. It examines the connections between convents and local musicians and the nuns’ taste for liturgical polyphony and villancicos. The convent music sources are analyzed within their devotional and liturgical context, particularly with regard to the universal Catholic feasts of Corpus Christi and Holy Week. I also consider convent-specific ceremonies such as nuns’ initiations. These events could be linked to urban patronage, as demonstrated through my discussion of the recruitment and selection process of musically trained women that could serve the convents as performers for the liturgies. This dissertation is the first to address Novohispanic convent music sources from the Newberry Library, CENIDIM, and the Museo del Carmen in a study about the Conceptionist convents that owned these manuscripts. The Conceptionist nuns were the first and wealthiest order of women religious to arrive in the New World and the only order in New Spain whose convents left behind polyphonic music. This study thus contributes to our understanding of women’s musical lives in broader Latin America, which have largely been marginalized in music history.