Gopalacampu 1.18.100

1.18.100

tatra ca-
tūkāraḥ khalu māthureṣu paritas tvaṅkāra-bhāṣā matā
so' yaṃ vaiṇava-gānataḥ pratipadaṃ prāyaḥ parāmṛśyate |
pratyekaṃ yugapat priyāṃ niśamayan kṛṣṇo yadā taṃ jagau
matvā svaṃ prati tat pratisvam api tāḥ sarvā vimūrcchāṃ yayuḥ || [śārdūla]

And there: / The sound 'tū' is indeed considered around Mathurā to be the language of addressing someone as 'thou' (tvaṅkāra); / and that was mostly brought out at every step through the song of the flute. / When Kṛṣṇa sang it, making each beloved hear it simultaneously, / all of them, each thinking it addressed to herself, fell into a faint.