Narapatijayacarya 3.1.3.5

3.1.3.5

athāyanasvaracakram
akāro dakṣiṇe svāmī ikāścottarāpaṇe ||
varṣabhuktyardhamānena bhogaḥ ṣāṇmāsikasvare ||

Now, the Solstitial Half-Year Sound Wheel: / The sound "a" is the ruler in the southern [course], and the sound "i" in the northern course; / by half the measure of the annual experience, the enjoyment takes place in the six-month sound.