Aitareya Āraṇyaka 2.3.4

2.3.4

yo ha vai yajñe yajñaṃ vedāhany ahar deveṣu devam adhyūḷhaṃ, sa saṃprativit \
eṣa vai yajñe yajño 'hany ahar deveṣu devo 'dhyūḷho, yad etan mahad uktham \
tad etat pañcavidhaṃ.
trivṛt pañcadaśaṃ saptadaśam ekaviṃśaṃ pañcaviṃśam iti stomato.
gāyatraṃ rathantaraṃ bṛhad bhadraṃ rājanam iti sāmato.
gāyatry u/ṣṇig bṛhatī triṣṭub dvipadeti chandastaḥ.
śiro dakṣiṇaḥ pakṣa uttaraḥ pakṣaḥ puccham ātmety ākhyānam \
pañcakṛtvaḥ prastauti.
pañcakṛtva udgā/yati.
pañcakṛtvaḥ pratiharati.
pañcakṛtva upadravati.
pañcakṛtvo nidha/nam upayanti.
tat stobhasahasraṃ bhavati \
evaṃ hy etāḥ pañca vidhā anuśasyante.
yat prāk tṛcāśītibhyaḥ, saukā vidhā.
tisras tṛcāśītayo.
yad ūrdhvaṃ, sā pañcamī \
tad etat sahasraṃ.
tat sarvaṃ.
tāni daśa daśeti vai sarvam.
etāvatī hi saṃkhyā.
daśa daśatas, tac chataṃ.
daśaśatāni, tat sahasraṃ.
tat sarvam \
tāni trīṇi chandāṃsi bhavanti.
tredhāvihitaṃ vā idam annam, aśanaṃ pānaṃ khādas.
tad etair āpnoti \\ 4 \\

He who knows one sacrifice above another, one day above another, one deity above the others, he is clever. Now this great uktha (the nishkevalya-sastra) is the sacrifice above another, the day above another, the deity above others.

This uktha is fivefold. With regard to its being performed as a Stoma (chorus), it is Trivrit, Pañkadasa, Saptadasa, Ekavimsa, and Pañkavimsa. With regard to its being performed as a Sâman (song), it is Gâyatra, Rathantara, Brihat, Bhadra, and Râgana. With regard to metre, it is Gâyatrî, Ushnih, Brihatî, Trishtubh, and Dvipadâ. And the explanation (given before in the Âranyaka) is that it is the head, the right wing, the left wing, the tail, and the body of the bird. in each hymn. This, is the first round. He then sings the three middle verses in each hymn. This is the second round. He lastly sings the last three verses in each hymn. This is the third round. This song is called Udyatî.
The Pañkadasa stoma is formed out of one Sûkta only, consisting of three verses. In the first round he sings the first verse three times, the second and third once. In the second round he sings the middle verse three times, in the third round he sings the last verse three times. This song is called Vishtuti.
The Saptadasa stoma is formed in the same manner, only that in the first round he sings the first verse three times, in the second the middle verse three times, in the third round the middle and last verses three times. This song is called Dasasapta.
The Ekavimsa stoma is formed in the same manner, only that in the first round he sings the last verse once, in the second the first verse once, in the third the middle verse once, while the other verses are each repeated three times. This song is called Saptasaptinî.
The Pañkavimsa stoma is formed in the same manner, only that in the first round he sings the first verse three times, the second four times, the last once; in the second round the first once, the second three times, the third four times; in the third round the first five times, the second once, the last three times; or he sings in the third round the first verse four times, the second twice, the last three times.
Sâyana in his commentary on the Ait. Âr. takes the Trivrit stoma to be formed out of three hymns, each consisting of three verses, while he says that the other stomas are formed out of one hymn only. B. and R., sv. trivrit, state that this stoma consists of verses 1, 4, 7; 2, 5, 8; and 3, 6, 9 of the Rig-veda hymn IX, 11, but, according to Sâyana, the stoma consists (1) of the first verses of the three Sûktas, upâsmai gâyata, davidyutatyâ, and pavamânasya at the beginning of the Sâma-veda-Uttarârkika, (2) of the second, (3) Of the third verses of the same three hymns. Mahîdhâra (Yv. X, 9) takes the same view, though the MSS. seem to have left out the description of the second paryâya, while Sâyana in his commentary to the Tândya-brâhmana seems to support the opinion of B. and R. There is an omission, however, in the printed text of the commentary, which makes it difficult to see the exact meaning of Sâyana.
The Pañkadasa stoma is well described by Sâyana, Tândya Br. II, 4. Taking the Sûkta agna â yâhi (Uttarârkika I, 1, 4 = Rv. VI, 16, 10-12), he shows the stoma to consist of (1) verse 1 × 3, 2, 3 (2) verse 1, 2 × 3, 3; (3) verse 1, 2, 3 × 3.
The five Sâmans are explained by the commentator. The Gâyatra is formed out of the Rik (III, 62, 10) tat savitur varenyam. The Rathantara is formed out of the Rik (VII, 32, 22) abhi tvâ sûra nonuma. The Brihat is formed out of the Rik (VI, 46, 1) tvâm id dhi havâmahe. The Bhadra is formed out of the Rik (X, 57, 1) imâ nu kam. The Râgana is formed out of the Rik (VII, 27, 1) indram naro nemadhitâ.
The metres require no explanation.
In identifying certain portions of the Nishkevalya hymn with a bird, the head of the bird corresponds to the hymns indram id gâthinah, &c.; the right wing to the hymns abhi tvâ sûra, &c.; the left wing to the hymns tvâm id dhi, &c.; the tail to the hymns imâ nu kam, &c.; the body to the hymns tad id âsa, &c. All this was explained in the first Âranyaka.

He performs the Prastâva in five ways, he performs the Udgîtha in five ways, he performs the Pratihâra in five ways, he performs the Upadrava in five ways, he performs the Nidhana in five ways. All this together forms one thousand Stobhas, or musical syllables.

Thus also are the Rik verses, contained in the Nishkevalya, recited (by the Hotri) in five orders. What precedes the eighty trikas, that is one order, then follow the three sets of eighty trikas each, and what comes after is the fifth order.

This (the hymns of this Sastra) as a whole (if properly counted with the Stobha syllables) comes to one thousand (of Brihatî verses). That (thousand) is the whole, and ten, ten is called the whole. For number is such (measured by ten). Ten tens are a hundred, ten hundreds are a thousand, and that is the whole. These are the three metres (the tens, pervading everything). And this food also (the three sets of hymns being represented as food) is threefold, eating, drinking, and chewing. He obtains that food by those (three numbers, ten, hundred, and thousand, or by the three sets of eighty trikas).