नक्षत्रान्येवर्क्चन्द्रमाः साम तदेतदेतस्यामृच्यध्यूढं साम तस्मादृच्यध्यूढं साम गीयते नक्षत्राण्येव सा चन्द्रमा अमस्तत्साम ॥ १.६.४ ॥
nakṣatrānyevarkcandramāḥ sāma tadetadetasyāmṛcyadhyūḍhaṃ sāma tasmādṛcyadhyūḍhaṃ sāma gīyate nakṣatrāṇyeva sā candramā amastatsāma || 1.6.4 ||
4. The stars are the Ṛk, and the moon is the Sāma. This Sāma [called the moon] is based on the Ṛk [called the stars]. This is why Sāma scholars sing songs based on the Ṛk. The stars are the sā, and the moon is ama. Together they are Sāma.
Word-for-word explanation:
Nakṣatrāṇi era ṛk, the stars together constitute the Ṛk; candramāḥ sāma, the moon is the Sāma; tat etat sāma, that Sāma; etasyām ṛci adhyūḍham, is based on the Ṛk; tasmāt, that is why; ṛci adhyūḍham sāma gīyate, the Sāma scholars sing the Sāma based on the Ṛk; nakṣatrāṇi eva sā, the stars are the sā; candramaḥ amaḥ, the moon is the ama; tat sāma, that [if joined together] is Sāma.
Commentary:
The moon is the lord of the stars. This is why it is given the status of the Sāma Veda.