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Kātyāyana's Sarvānukramaṇi (ca. 2nd century BCE), records the first word, the number of verses, name and family of poets (r̥ṣi-s), names of deities and
metres for each of the 1,028 hymns of the R̥gveda. Vedārthadipika, written by SadguruŚiṣya (12th century) has quotations from six Anukramaṇis of the R̥gveda ascribed to Śaunaka: Anuvākanukramaṇi, Arṣānukramaṇi,
Chandonukramaṇi, Devatānukramaṇi, Padānukramaṇi and Suktānukramaṇi. Clearly, r̥ṣi-s spread over atleast three generations, before the Samhitā was organized and compiled. (Note. In my view, the number of generations of R̥gveda r̥ṣi-s is guesswork and cannot be precisely determined).
This organization of the sacred oral texts into R̥gveda Samhitā is clearly seen to present an integrated, comprehensive compilation -- including Sāmaveda -- as evident from the reference to tri sapta (3x7 = 21) in RV 1.72.6 and in RV 10.90.15.
Thus, it will be an error to state that R̥gveda Samhitā is antecedent to Sāmaveda, because the following r̥ca-s clearly include prayers of Sāmaveda as an integral part of the R̥gveda Samhitā:
Kātyāyana's Sarvānukramaṇi (ca. 2nd century BCE), records the first word, the number of verses, name and family of poets (r̥ṣi-s), names of deities and
metres for each of the 1,028 hymns of the R̥gveda. Vedārthadipika, written by SadguruŚiṣya (12th century) has quotations from six Anukramaṇis of the R̥gveda ascribed to Śaunaka: Anuvākanukramaṇi, Arṣānukramaṇi,
Chandonukramaṇi, Devatānukramaṇi, Padānukramaṇi and Suktānukramaṇi. Clearly, r̥ṣi-s spread over atleast three generations, before the Samhitā was organized and compiled. (Note. In my view, the number of generations of R̥gveda r̥ṣi-s is guesswork and cannot be precisely determined).
This organization of the sacred oral texts into R̥gveda Samhitā is clearly seen to present an integrated, comprehensive compilation -- including Sāmaveda -- as evident from the reference to tri sapta (3x7 = 21) in RV 1.72.6 and in RV 10.90.15.
Thus, it will be an error to state that R̥gveda Samhitā is antecedent to Sāmaveda, because the following r̥ca-s clearly include prayers of Sāmaveda as an integral part of the R̥gveda Samhitā:
Trans. (Wilson) 1.072.06 (Devout men), competent to offer sacrifices, have known the thrice seven mystic rites comprised in you, and with them, worshipped you; do you, therefore, with like affection, protect their cattle, and all that (belongs to them), moveable or stationary. [gr.hya_n.i pada_ (ni): secret or mysterious steps by which heaven is said to be obtained. Ceremonies of vedas (all involving Agni) are in three classes, each class has seven yajn~as: pa_ka-yajn~as, those in which food of some kind is offered (aupa_sana, homa, vais'vadeva); havir-yajn~as, those in which clarified butter is offered (agnya_dheya, dars'a pu_rn.ama_sa); and soma-yajn~as, the principal part of which is the libation of soma (agnis.t.oma, atyagnis.t.oma)].
सायणभाष्यम्
त्रिः “सप्त एकविंशतिसंख्याकानि “गुह्यानि रहस्यानि वेदैकसमधिगम्यानि “यत् यानि “पदा पदानि । पद्यते गम्यते स्वर्गः एभिरिति व्युत्पत्त्या पदशब्देनात्र यज्ञा उच्यन्ते । ते चैकविंशतिसंख्याकाः। औपासनहोमवैश्वदेवादयः सप्त पाकयज्ञाः । अग्न्याधेयदर्शपूर्णमासादयः सप्त हविर्यज्ञाः । अग्निष्टोमात्यग्निष्टोमादयः सप्त सोमयज्ञाः । एवमेकविंशतिसंख्याकानि यज्ञलक्षणानि पदानि हे अग्न “त्वे “इत् त्वय्येव “निहिता स्थापितानि । तेषां सर्वेषां त्वत्प्रधानत्वात्। न ह्यग्निमन्तरेण यागा अनुष्ठातुं शक्यन्ते। “यज्ञियासः यज्ञार्हाः अर्थित्वसामर्थ्यवैदुष्यादिभिः'अधिकारहेतुभिर्युक्ताः। तथा चोक्तम्-‘अर्थी समर्थो विद्वान् शास्त्रेणापर्युदस्तः कर्मण्यधिकारी'इति । एवंविधलक्षणोपेता यजमानास्तानि पदानि "अविदन् अलभन्त । लब्ध्वा च "तेभिः यज्ञलक्षणैः पदैः "अमृतम् अमरणधर्माणं त्वां “रक्षन्ते पालयन्ति यजन्तीत्यर्थः। “सजोषाः । तैर्यजमानैः समानप्रीतिस्त्वं “पशून् गवाश्वादिपशून् “च "स्थातॄन् व्रीह्यादिस्थावराणि “चरथं पशुव्यतिरिक्तमन्यद्यत्प्राणिजातमस्ति तत् “च "पाहि रक्ष । तेषु हि रक्षितेषु त्वदीया यागाः कर्तुं शक्यन्ते नान्यथा । अतस्त्वमेवमुच्यसे इत्यर्थः ॥ यत् । 'सुपां सुलुक्'इति विभक्तेर्लुक् । गुह्यानि । गुहायां भवानि ।'भवे छन्दसि 'इति यत् । ‘ यतोऽनावः'इत्याद्युदात्तत्वम् । त्वे। ‘सुपां सुलुक् 'इति सप्तम्याः शेआदेशः । अविदन् । 'विद्लृ लाभे'। लुङि लृदित्वात् अङ् । पशून स्थातॄन् । उभयत्र 'उभयथर्क्षु ' (पा. सू. ८. ३. ८) इत्युभयथाभावात् नकारस्य रुत्वाभावः ॥
Trans. (Wilson) 10.090.15 Seven were the enclosures of the sacrifice, thrice seven logs of fuel were prepared, when the gods, celebrating the rite, bound Purus.a as the victim. [Seven enclosures: sapta paridhayah = seven metres, ga-yatri_ etc., and also as meaning the shallow trenches, three of which were dug round the A_havani_ya fireplace, three round the northern altar, and the seven ideally dug round the sun to keep off evil spirits. paridhayah = moats; or, the seven oceans; thrice seven pieces of fuel = twelve months of the year, the five seasons, the three worlds and the sun; or the three classes of seven metres eaach: Taittiri_ya Sam.hita_5.1.10.3].
Trans. by Seven Nepali pandits in Bhavan's Rig Veda Samhitā ed. Prasana Chandra Gautam, 2014: Spreading to which Yagnya the god had tied that primordial Purusha as the sacrificial animal for that Yagnya, the boundaries of that Yagnya were seven metres and the twenty one fire woods had been prepared. Essence: Twenty one types of Yagnyas in three groups were established in which prayers were said in seven metres (See Mantra No. 822 Mandal 1, i.e. 1.72.6 transcribed above).
सायणभाष्यम्
अस्य सांकल्पिकयज्ञस्य गायत्र्यादीनि “सप्त छन्दांसि परिधयः “आसन् । ऐष्टिकस्याहवनीयस्य त्रयः परिधय उत्तरवेदिकास्त्रय आदित्यश्च सप्तमः परिधिप्रतिनिधिरूपः । अत एवाम्नायते-- न पुरस्तात्परि दधात्यादित्यो ह्येवोद्यन् पुरस्ताद्रक्षांस्यपहन्ति' (तै. सं. २.६.६.३) इति । तत एत आदित्यसहिताः सप्त परिधयोऽत्र सप्त छन्दोरूपाः । तथा “समिधः “त्रिः सप्त त्रिगुणीकृतसप्तसंख्याकाः एकविंशतिः “कृताः । द्वादश मासाः पञ्चर्तवस्त्रय इमे लोका असावादित्य एकविंशः ( तै. सं. ५.१.१०.३) इति श्रुताः पदार्था एकविंशतिदारुयुक्तेध्मत्वेन भाविताः। यत् यः पुरुषो वैराजोऽस्ति ते “पुरुषं "देवाः प्रजापतिप्राणेन्द्रियरूपाः यज्ञं तन्वानाः मानसं यज्ञं तन्वानाः कुर्वाणाः पशुम् "अबध्नन् विराट्पुरुषमेव पशुत्वेन भावितवन्तः । एतदेवाभिप्रेत्य पूर्वत्र ‘ यत्पुरुषेण हविषा'इत्युक्तम् ॥
What are these 21 types of yagnyas in three groups? Three groups of yagnyas are: पाकयज्ञ, हविर्यज्ञ, सोमयज्ञ.
The three groups of Yagnya with seven different forms of Agni in each group, are as follows:
पाकयज्ञ: औपासन होम, वैश्वदेव, पाक्षिक स्थालीपाक, श्रवणाकर्म, आएवयुजी, आग्रहायणी, अष्टका
हविर्यज्ञ: अग्न्याधान, अग्निहोत्र, दर्शपौर्णमास, पिण्डपितृयज्ञ, आग्रयण, चातुर्मास्य, पशुबन्ध
सोमयज्ञ: अग्निष्टोम, अत्यग्निस्टोम, उक्थ्य, षोडशी, वाजपेय, अतिरात्र, अप्तोर्याम
Thus, it is seen that the 21 different forms of Agni/Yagnya are firmly established in the R̥gveda Samhitā. I will not venture to determine the date of R̥gveda
Samhitā and the number of generations of r̥ṣi-s whose mantra-s are included in the compilation, except to state that the mantra-s have been transmitted from generation to generation with high-fidelity and include clear references to the Sāmaveda mantra-s.