For mod12, pitch classes can be either numbers or letter names (either uppercase or lowercase, with '#' for sharp and 'b' for flat). For all other moduli only numbers are allowed.

The decimal number is a numeric representation of the set used for identification, much like the Forte set-class numbers. It is the sum of 2^x for all pitch classes x in the set. For example, the set {0, 1, 4, 6} is represented by the number:
2⁰ + 2¹ + 2⁴ + 2⁶ = 83.