This interesting writing-up i found at this blog by Sriram V. This was Sumathi Krishnan’s topic for lec-demonstration at the Music Academy on 17th December 2010. She is a senior disciple of R Vedavalli. According to her, the earliest traceable varnam is that of Govindasamayya, a composer of the 17th century. Early varnams appear to have largely been in Telugu and later there have been Sanskrit, Tamil, Malayalam and Kannada varnams as well.
Varnams appear to have grown in volume over the years. The Sangita Sarvartha Sara Sangrahamu of Veena Ramanujayya has only 12 in its 1885 edition. There are 25 in Pallavi Svarakalpavalli (1900) which has the compositions of Veena Kuppayyar and Tiruvottiyur Tyagier. There are 40 varnams in the Sangita Sampradaya Pradarsini of Subbarama Dikshitar (1904). In TK Govinda Rao’s Varnasagaram (2006) there are 500 and in the Tana Varna Tarangini of BM Sundaram there are 806.
Varnams appear to have been a standard method of praising royalty. There are varnams in praise of Serfoji and other Marathas (by Pacchimiriyam Adiyappayyah, Pallavi Gopala Iyer and Panchanada Sastry, the father of Patnam Subramania Iyer), Swati Tirunal (by Palghat Paramesvara Bhagavatar, Vadivelu), Ettayapuram family (Balaswami Dikshitar and Subbarama Dikshitar), the Wodeyars (Mysore Sadasiva Rao, Veena Subbanna and Seshanna, Harikesanallur Muthiah Bhagavatar), the Rajahs of Ramnad (Subbarama Dikshitar, Poochi Iyengar, Kunrakkudi Krishna Iyer).
The structure of a varnam is usually pallavi, anupallavi, muktAyi svaram, caraNam, eDDugaDa svarams. But there are variants, for example Ramaswami Dikshitar’s svarasthAna varnam in tODi in praise of Manali Venkatakrishna Mudaliar has only pallavi, anupallavi, caraNam and the svaras for the last named.
Swarasthana Pada Varnam of Ramaswamy Dikshitar in Todi ragam and Adi thalam. The sahityam uses only the seven letters "sa, ri, ga , ma pa, dha and ni", all of Todi.
sarigAni dAni pAmarini nI pada
garimamadAri padAri sadAri
gamapadAnigA nidAni pasagani
marimari ganisAga nipani dagadani
mari nI pathama manigAmarEnigA
manali venkatakrishnendra nAto
Padajati varnams are those that have jatis svarams in the muktAyi portion. Examples are Kunrakkudi Krishna Iyer’s varnam in kEdAram and Muthiah Bhagavatar’s mAtE (khamAs).
The older varnams have a sAhitya portion after the svaras are sung. This is today called the anubandam though earlier texts do not use this term.
The choice of ragas for varnams is quite varied. Some of the rare ragas are Ahiri (used by Tarangampadi Panchanada Iyer), asAvEri and kannaDa by Patnam Subramania Iyer, nArAyaNa gauLa and gauLa (Veena Kuppayyar), sAma and dEvamanohari (Kothavasal Venkatarama Iyer).
There are rAgamAlika varnams such as the most famous valaji in nine ragas. But a more interesting example presented was Vinjamuri Varadaraja Iyengar’s ghana rAga pancaka varnam where the pallavi is in nATa, the anupallavi in gaula, the muktAyi in Arabhi, the first caraNam in varALi (did she say shri is in the second caraNam?) and all five ragas appear in the last caraNam. Veena Venkatesvara Raja’s varnam has the first three as in Vinjamuri’s but the caraNams have ragas from the second set of ghana ragas – bhauLi, kEdAram, nArayaNa gauLa. The behAg varnam of Veena Seshanna has the last eDDugaDa in 14 ragas.
A variety of talas have been used in varnams. Veena Seshanna has used khaNDa dhruva, misra jhampa, khaNDa triputa, khaNDa maTya and misra tripuTa. Tanjavur Ponniah Pillai has used tisra aTa. Subbarama Dikshitar has used rUpakam, tisra Ekam. Kunrakkudi Krishna Iyer has used misra jhampa. Poochi Iyengar has used catusra aTa and Mudicondan has used tisra dhruvam.
There are varnams based on metre/chandas as well. Thus a varnam in navroj has several metres such as matta ibha, dvipada, utpala and campakamAla.
The cauka varnam is a term that is based on tempo and even pada varnams can be cauka varnams.
When it comes to svara patterns, varnam composers would appear to have used their imagination to the fullest. There are varnams with vAdi samvAdi usage (gAga nini usages in Muthiah Bhagavatar’s mAtE). The same note in different sthAyis is used for instance by Kothavasal Venkatarama Iyer in his sAma varnam. The same note is repeated to good effect by Subbarama Dikshitar in his nATa varnam. The kAmboji varnam of Maha Vaidyanatha Sivan displays usage of mridanga, gopuccha and pippilika (sama) yatis. The suruTTi varnam of Subbarama Dikshitar has svarAkshara with the caraNam lines starting with the same syllable as the svaras to which they are set.
Some varnams have sangatis as well. While many have been extrapolations by later day musicians, some appear in the early texts as well. An instance is the manohari varnam of Ramaswami Dikshitar. There is a varnam in kharaharapriya by Mudicondan Venkatarama Iyer and this has sangatis too.