In a bahuvrīhi samāsa the acute accent (udātta) does not fall on such mukha 'mouth' denoting a real mouth when it comes after an indeclinable and a name of a direction or after 1. go 2. mahat 3. sthūla 4. muṣṭi 5. pṛthu and 6. vatsa,
Thus: अव्ययः - उच्चै꣡र्मुखः, नीचै꣡र्मुखः ॥ The words उच्चैः and नीचैः are finally acute and retain their accent. दिक् - प्रा꣡ङ्मुखः, प्रत्य꣡ङ्मुखः ॥ The word प्राङ् has acute on the first by 6.2.52, and प्रत्यङ् is finally acute by 6.3.139. गो &c :- गो꣡मुखः, महा꣡मुखः, स्थूल꣡मुखः, मुष्टिमु꣡खः पृथु꣡मुखः and वत्स꣡मुखः ॥ In these the first members of the Bahuvrihi preserve their respective accents under Rule 6.2.1 and in the case of compounds preceded by गो, मुष्टि and वत्स, the optional rule taught in the next sutra is also superseded by anticipation, though the words may denote comparison.,