I bet you didn't know that math was used in music but you know what, it is. When dealing with sound people are constantly using frequency. The unit for frequency is called Hertz. (abbr. hz) Is the reciprocal of one second. It makes sense because when you think about it the period of a cyclical process is equal to one over the frequency. (p=1/f) Frequencies are discussed in thousand of Hertz, the unit of kiloHertz (1000hz=1khz) is very useful.