BṚHADĀRAṆYAKA UPANISHAD · 1.3.25

तस्य हैतस्य साम्नो यः स्वं वेद भवति हास्य स्वम् ।
तस्य वै स्वर एव स्वम् ।
तस्माद् आर्त्विज्यं करिष्यन् वाचि स्वरम् इच्छेत ।
तया वाचा स्वरसम्पन्नयार्त्विज्यं कुर्यात् ।
तस्माद् यज्ञे स्वरवन्तं दिदृक्षन्त एव ।
अथो यस्य स्वं भवति ।
भवति हास्य स्वं य एवम् एतत् साम्नः स्वं वेद ॥

tasya haitasya sāmno yaḥ svaṃ veda bhavati hāsya svam ।
tasya vai svara eva svam ।
tasmād ārtvijyaṃ kariṣyan vāci svaram iccheta ।
tayā vācā svarasampannayārtvijyaṃ kuryāt ।
tasmād yajñe svaravantaṃ didṛkṣanta eva ।
atho yasya svaṃ bhavati ।
bhavati hāsya svaṃ ya evam etat sāmnaḥ svaṃ veda ॥

He who knows what is the property of this Sâman, obtains property. Now verily its property is tone only. Therefore let a priest, who is going to perform the sacrificial work of a Sama-singer, desire that his voice may have a good tone, and let him perform the sacrifice with a voice that is in good tone. Therefore people (who want a priest) for a sacrifice, look out for one who possesses a good voice, as for one who possesses property. He who thus knows what is the property of that Sâman, obtains property.

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)