Pitch Class
Sets of notes with the same name that are some number of octaves apart from each other
A pitch class groups all pitches that are a whole number of octaves apart and gives them one name. C2, C3, C4, and C5 are different pitches but the same pitch class, C. This works because notes an octave apart are perfectly consonant: their frequencies combine without muddying the sound.
In NoSheet, each pitch class has a consistent color across every instrument and challenge. Every noteset can be described as a set of pitch classes, one of which is the root.