Jaiminīya Upaniṣad Brāhmaṇa 3.37.6

3.37.6

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

He is this Indra, the udgītha. When this Indra, the udgītha, arrives, neither [the voice] of the udgātṛ nor of the accompanying choristers is distinguished. Directly from here upward rises the tone; it vibrates above the crown of the head.