Viṣṇu-bīja ('a') + 3rd letter of 2nd group ('g') forms svara
Body (pseudocode)
COMPOSE svara FROM concat(third_letter(group_2)='g', viṣṇu_bīja='a') = 'ga'
Inputs / output
consonant=g
—
vowel=a
—
→ svara_syllable
Evidence (1)
p. vol_I_p032 · #2328« The third (letter) of the second group (viz. 'g') combined with Viṣṇu-bīja, (viz. 'a'), one should always draw out (this) svara »