Bhashya
सर्वे स्वरा अकारादय इन्द्रस्य बलकर्मण प्राणस्यआत्मान देहावयवस्थानीया ।सर्वे ऊष्माण शषसहादयप्रजापतेर्विराज कश्यपस्य वा आत्मान ।सर्वे स्पर्शाकादयो व्यञ्जनानि मृत्योरात्मान ।तमेवविद्मुद्गातार यदिकश्चित् स्वरेषूपालभेत- स्वरस्त्वया दुष्ट प्रयुक्त इति, एवमुपालब्ध इन्द्र प्राणमीश्वर शरणम् आश्रय प्रपन्नोऽभूवस्वरान्प्रयुञ्जानोऽहम्, स इन्द्र यत्तव वक्तव्य त्वा त्वा प्रतिवक्ष्यति स एव देव उत्तर दास्यतीत्येन ब्रूयात् ॥
In plain words
All vowels, beginning with 'a', are the forms of Indra—who is breath, strength, and action—constituting his bodily limbs. All sibilants, beginning with ś, ṣ, s, and h, are the forms of Prajāpati, or Virāj, or Kaśyapa. All stop consonants, beginning with 'k', are the forms of Death. If someone should criticize the udgātṛ who knows this, saying, 'Your vowel was pronounced incorrectly,' when thus criticized he should tell him: 'I have taken refuge in Indra, the lordly life-breath, while uttering the sounds. That very deity Indra will give you your answer concerning what needs to be said to you.'
Close to the Sanskrit
All vowels beginning with 'a' are selves of Indra of strength-action of breath, as body-parts. All sibilants beginning with śa, ṣa, sa, ha are selves of Prajāpati of Virāj of Kaśyapa or. All stops beginning with 'ka' as consonants are selves of Death. That same-knowing udgātṛ if someone should criticize in vowels—'sound by thee flawed used'—thus criticized, Indra life-lord refuge shelter approached I became, vowels employing I, that Indra what is to be spoken, thee thee towards will speak, he indeed deity answer will give, thus to him one should speak.