Jaiminīya Upaniṣad Brāhmaṇa 1.45.4

1.45.4

sa eṣa indra udgīthaḥ
sa yadaiṣa indra udgītha āgacchati naivodgātuś copagātṝṇāṃ ca vijñāyate
ita evordhvas svar udeti
sa upari mūrdhno lelāyati /

This Indra is the udgītha. When this Indra, the udgītha, arrives, neither the udgātṛ's nor the assistant chanters' [voice] is distinguished; rising upward from here, svaḥ goes up; it flickers above the head.