BṚHADĀRAṆYAKA UPANISHAD · 4.5.10

स यथा वीणायै वाद्यमानायै न बाह्याञ् छब्दाञ् छक्नुयाद् ग्रहणाय ।
वीणायै तु ग्रहणेन वीणावादस्य वा शब्दो ग्र्हीतः ॥

sa yathā vīṇāyai vādyamānāyai na bāhyāñ chabdāñ chaknuyād grahaṇāya ।
vīṇāyai tu grahaṇena vīṇāvādasya vā śabdo grhītaḥ ॥

'And as the sounds of a lute, when played, cannot be seized externally (by themselves), but the sound is seized, when the lute is seized, or the player of the lute;