CC Antya 2.155

manuṣya nā dekhe — madhura gīta-mātra śune
govindādi sabe meli’ kaila anumāne
Synonyms: 
manuṣya — a man; dekhe — could not see; madhura — very sweet; gīta — singing; mātra — only; śune — one could hear; govinda-ādi sabe — all the devotees, headed by Govinda; meli’ — coming together; kaila anumāne — guessed.
Translation: 
No one could see him, but they could hear him singing in a sweet voice. Therefore all the devotees, headed by Govinda, made this guess.