For instance, the A is tuned such that its frequency equals 3/2 times the frequency of D—if D is tuned to a frequency of 288 Hz, then A is tuned to 432 Hz. Similarly, the E above A is tuned such that its frequency equals 3/2 times the frequency of A, or 9/4 times the frequency of D—with A at 432 Hz, this puts E at 648 Hz. Since this E is outside the above-mentioned basic octave (i.e. its frequency is more than twice the frequency of the base note D), it is usual to halve its frequency to move it within the basic octave. Therefore, E is tuned to 324 Hz, a 9/8 (= one epogdoon) above D. The B at 3/2 above that E is tuned to the ratio 27:16 and so on. Starting from the same point working the other way, G is tuned as 3/2 below D, which means that it is assigned a frequency equal to 2/3 times the frequency of D—with D at 288 Hz, this puts G at 192 Hz. This frequency is then doubled (to 384 Hz) to bring it into the basic octave.