All throughout, Cassandra repeatedly connects frequencies to notes. However, the frequencies discussed are all in the terahertz range (trillions of cycles per second), while the entire range of human hearing is from around 25 Hz to 25 kHz. In one example, she cites 440 tHz as high A. The A above middle C is 440 Hz, with the frequency doubling for every octave, so high A is 880 Hz.