अन्तरिक्षमेवर्ग्वायुः साम तदेतदेत-स्यामृच्यध्यूढं साम तस्मादृच्यध्यू-ढं साम गीयतेऽन्तरिक्षमेव सा वायु-रमस्तत्साम ॥ २ ॥
In plain words
The atmosphere itself is the ṛk verse, and the wind is the sāman chant. Because this sāman rests upon that ṛk, the sāman is sung as resting upon the ṛk. The atmosphere indeed is the verse, and the wind is the chant.
Close to the Sanskrit
The atmosphere alone is the ṛk, wind is the sāman; that this sāman is supported upon this ṛk, therefore the sāman is sung supported upon the ṛk. The atmosphere indeed is that (ṛk), wind is the sāman, that is sāman.