Chant initially appeared as liturgical music of the Latin Church. It originated in Jerusalem in the fourth century and further developed in Rome during the seventh century (Tibbetts & Saffle, 2018). By the end of the Middle Ages, it already existed in various forms and served distinct religious traditions, even today remaining the norm for concert church music (Tibbetts & Saffle, 2018). Chant had a particular rhythmic structure, which became slower over time, and by the twelfth century, it became known as cantus planus.
By the ninth century, chant chanting took on the form of parallel intervals, which was common in many cultures. This type is called a parallel organum and depends “on the limitation of voices or on acoustic reinforcement” (Tibbetts & Saffle, 2018, p. 22). It is implied that all parts move in the same direction simultaneously but differ in pitch. Another type of organum is a technique when one voice sustains one pitch, and the other sings the chant melody above it (Tibbetts & Saffle, 2018). There are other types of organum, including harmonizing notes against the chant, note-against-note, then more than one note against each chant note. The history of the development of this musical direction documents many changes.
Polyphonic vocal writing shifted from works in which each voice sang its own text to ones in which all the voices sang the same words at basically the same time. Four distinct parts (rather than three) became the norm as this new style strengthened its grip on the musical world. Furthermore, individual parts were no longer as interchangeable as they had been in the past. The range was now a conscious factor in creating polyphonic music. Thus, in the Renaissance period, chants became a source of fixed materials for composition.
As a pedagogical tool, cantus firmus was used exclusively in Gradus ad Parnassum to teach counterpoint. As the Baroque era continued, performers moved to the forefront of new means of musical expression. Whether it was singers improvising striking passages in opera, keyboard players adding ornamentation to ordinary melodic lines, or organists creating expansive, spontaneous works based on hymn tunes. Contrapunctus IX in Bach’s Art of the Fugue recalls a pre-existing melody, rhythmically augmented against other faster-moving voices, used as the basis for that composition.
Reference
Tibbetts J.C., & Saffle M. (2018). Medieval and early modern music. In: J. Tibbetts et al. (Eds.), Performing music history (pp. 7-43). Palgrave Macmillan.