This chapter is the first of three that set out the basic building blocks of musical syntax in Renaissance music, beginning with those connected to pitch. The first section sets out the key concepts of music theory dating back to the time of Guido of Arezzo in the eleventh century, whose pertinence endures into the Renaissance (thus, the gamut, mode, the species of fourth and fifth, the so-called Guidonian Hand, and the hexachord). The next section lays out the complex (and at time fraught) relationship between these concepts and composed polyphony, laying bare in particular the tension between modes (which were initially adapted from Greek theory to classify plainchant) and polyphony. This is seen most obviously in the functioning of the most fundamental element of counterpoint, the cadence. The chapter concludes by considering other key elements of pitch-treatment, including musica ficta, dissonance treamtment, and enhanced or expanded chromatic practice.