The sidereal cycle of the Moon is 27.32 days and the synodic cycle, as viewed from Earth by us, is 29.53 days . Now 365.25, the number of earth days in a year divided by 29.53 gives 12.37 and if we multiply this by two, to allow for the waxing and waning phases of the Moon, we get 24.74. This to the nearest whole number 25 is the number of sparśa or the mute consonants. (See Table 1).
For the sidereal cycle we get similarly 26.74 ; the number of lunar constellations in the Vedic system is 27 and is listed in the reference . Each constellation marks thirteen degrees and twenty minutes of arc in the zodiac.
The Alphabet unfolds the sound energies or vāni as we view outwards from the Earth. This is called bhūgölik or earth-centric. If we view from the heavens downwards it is called khagölik – as seen from an external point of observation, and this gives rise to dhvani or music.
◊ The Taittirīya Upaniśad says right in the beginning (it is the 2nd shlöka of the Śīkśā Vallī, the first shlöka being the Śhānti pāth or the peace invocation of this particular Upaniśad) :-
aum śīksām vyākhyāsyāmah . varnah svarah . mātrā balam . sāma samtānah . ity + uktah śīksādhyāyah
This shlöka is more like a sūtra – a condensed form of a secret instruction :-