Thodayamangalam is invocatory item. In Vazhuvur style it is used as the first item in praise of Lord Gnyana Sabeshar of Vazhuvoor. Also it was used in Bhagavata Mela Natakam. Usually it is in praise of Vishnu and his incarnations.
Thodayamangalam is accompanied by melaprapti*: nattuvanar, vocalist, orchestra members (flute, mridangam, kanjeera, ghatam), who also sings OM besides playing.
*Melaprapti is rhythmic recital. In olden days each performance was started with it.
Here is the some notes i got from the article published in Sruti .
Singing of the set of five thodaya mangalam songs prior to the start of a solo Sadir recital was still in vogue in the early decades of this century. T. Sankaran, cousin of Balasaraswati, wrote in an article on the Tanjavur Quartet in the Hindu of March 2, 1970:
"The melaprapti from behind the curtains consisted of konnakkol** to the accompaniment of the nattuvanar’s cymbals and the clang of the mridangam, all in the khanda nadai. This convention used to be a wonderful preliminary thus building up the proper atmosphere for a dance recital. The curtain rose only after the thodaya mangalam in Nattai ragam heralded the dancer."
**Konakkol is the art of vocalising rhythmic syllable (sollukattu) in proper manner.
In the scheme of dance developed by the Tanjavur Quartet, the melaprapti was indeed obligatory as an overture. T. Balasaraswati mentioned the practice of melaprapti, which included the singing of the thodaya mangalam, in the exclusive interviews she gave to Sruti editors prior to her demise (Sturi No. 3, February 1984.) In her presidential address at the Tamil Isai Conference at the end of 1975, she omitted reference to the melaprapti and thodaya mangalam. probably because the thodaya mangalam is a prelude to and not a part of the dance recital, but more probably because the practice of melaprapti had been discontinued years earlier. The person who reportedly had taken the initiative to do so was guru Kandappa (Sruti No.3, February 1984), the guru of Balasaraswati.
If melaprapti, with the complementary thodaya mangalam, rendered as an .overture from behind the curtains prior to the start of a dance event is no longer in vogue, some dancers present a thodaya mangalam as the first choreographed item of their recitals. Dancers trained by the late Mangudi Dorairaja Iyer and Adyar Lakshman do so, for example. What they offer, however, are abridged versions of the thodaya mangalam, evidently because it would be time-consuming to dance to all the 70 lines of the original five songs (the most famous one is Jaya Janaki Ramana.)
Dancers of the Vazhuvoor school also present a thodaya mangalam, but this piece is a creation of the great nineteenth century nattuvanar who hailed from Vazhuvoor but was known as Tanjavur Swaminathan. It starts with the words "Jaya su bhrapurivasa, jaya mahajnana sameta", in Nattai. In its last line it contains the mudra of the composer, which is Bhakta Swaminathan. Swaminathan was the grandfather of Vazhuvoor Ramiah Pillai.
Kamala, Padma Subrahmanyam, Chitra Visweswaran and all the others who studied with Ramiah Pillai start their recitals with this particular thodaya mangalam.
Chitra Visweswaran says she has seen the song inscribed on the walls of the Vazhuvoor temple. The disciples of Swamimalai Rajarathnam and K.J. Sarasa, the gurus who were earlier associated with the Vazhuvoor tradition, also do the same. Ramiah Pillai claims he has composed many melaprapti jatis, but they are not in vogue now.
Many dancers have replaced the erstwhile melaprapti and thodaya mangalam with the rendering of invocatory verses or songs prior to the entrance of the dancer. Some sing Mahaganapatim in Nattai composed my Muthuswami Dikshitar or Vatapi Ganapatim in Hamsadhvani or Vinay aka ninu vina in Hamsadhvani composed by Kothavasal Venkatarama Iyer.
This composition belongs to the sphere of applied music. It figures in dance dramas. It is the story told in form of a song. In Daru the principal character of dance drama is praised and his deeds are described. Daru is sung in Madhyama kala (medium tempo).
Daru consists of Pallavi, Anupallavi (optional) and Charanam. In certain Daru there will be mixture of Jathis as well. Sahitya of Daru is simple. Subject of Daru is prayer, history, dialogue, commendation, etc. Daru is usually sung in Madhyama kala (medium speed). Daru are used in Villu Pattu, musical and dance dramas. There are different kinds of Darus: - Pravesika Daru: this song is meant to introduce those who take part in performance.
Keertanas deal with glories of the Gods. It includes Pallavi, Anupallavi and Charana-s. Keertanas are set to lighter ragas. It is usually sung in Madhyama kalam (medium tempo). Sahityam narrates prayers and stories from Puranas, thus basic bhava of keertanam is Bhakti.
As a dance composition, Keertanam is abhinaya item, where lines of sahityam are intervened with jathis and swaras during which the dancer executes different korvais (sets of adavus).
In Keertanam Sahityam (lyrics) takes predominant place. Sahityam concerns different deities and their devotees. Music is very simple, full of Raga Bhava. Keertanam contains only Pallavi, Charanams and swara patterns of charanams (varnamettu).
In certain Keertanas the charanam will be in the pallavi part itself (it is called "Samasti Charanam").
There are also composite keertanas. For example, Sri Tyagarajas Divyanama keertanas, Utsavasampradaya keertanas.
Sangeeta Pitamaha ("The Great Father of Music") Sri Purandaradasa composed many keertanas in Sanskrit and Kannada. They are called "Devarnama" (or "Devara Nama", names of God) or "Dasar Padams", as those Keertanas are full of Bhakti and Sringara bhava and thus stay close to Padams.
S Sharada Teacher explains Keertanam like that:
"Keertanas are taken from other works should be authentically presented. There is a common misconception that the keertanam "Yaro ivar yaro" is Sita singing about Rama, while in reality it is Rama singing about Sita*. The kalapramanam should be moderate. Rukmini Devi used to say that abhinaya should be done to slow kalapramanam in order to create an impression of wanting to make it slower."
*This wonderful keertanam is sung in Bhairavi ragam, very deep, touching and rich of moods raga. In this keertanam Rama comes to garden along with Lakshmana and encounters Sita first time. He is stunned and taken by overwhelming feeling of attraction and admiration towards her. He asks "Yaro ivar yaro? Enna pero narien?" - "Who is she? What is her name?"
In music, keerthnam is a composition stressing on sahitya (lyrics), set to melodious tune, which is comparatively simple. Here, sahitya bhavam is emphasized, and raga bhava (music) is given the second place.
In dance any composition having sahitya arranged in pallavi-anupallavi-caranam format is termed as a keerthnam (apart from padam, javali and ashrapadi).
This could also include compositions that are referred to as “krti" in music.
For example, "ananda natamaduvar tillai" in Raga Purvikalyani by Nilakantha Sivan or "varugalamo" in Raga Majji by Gopalakrsna Bharati or "devi niye tunai" in Kiravani by Papanasam Sivan or "Ananda nanana prakasam" in Kedaram by Muddusvaami Dikshita are also termed as keerthnam in dance.
Abhinaya in a keerthnam it is mostly descriptive in nature, it may include elaborate sancari bhavas or not. There is the one difference here from Padam, Javali and Ashtapadi: the major bhavam of keerthanam is bhakti (not Sringara), thus abhinaya of keerthnam is not of Nayaka-Nayaki Bhava (in majority of cases).
Bajanas are traditional devotional songs. They oridinated in North India and are widely accepted now because melody is usually pleasing and simple, sahityam (lyrics) is purely religious, full of elevated devoutional feelings.
Immortal creations of Jayadeva, multi-layered and multi-faceted, dramatic and deep, born from irresistable music, reflection all shades of emotions evoked by powerful feeling of love.
Ashtapadis of Jayadeva are contained in "Gita Govindam" (see also "Gita Govinda Dance Drama"). The book is divided in twelve chapters. Each chapter describes different stages of human love. They believe that JAyadeva delineated the concept of Jivatama-Paramatma, when human soule (jiva atma) is in serach of Parama atma (Universal soul) and salvation.
According to (2), "In Jayadevas environment of spring time (sarasavasanta), Radha and Krishna are vehicles for the unversalization of erotic emotion. These youthful figures with gleaming flesh and lotus-petal eyes manifest signs of emotion to communicate passion for their separation. For Jayadeva, their longing and reunion is the concrete example of religious experience in which the disquieting distinction between "I" and "mine" versus "you" and "yours" is calmed. The esthetic experience of their love is the means for breaking the imaginary barrier dividing human from divine."
"In Gitagovinda, Radha is neither a wife nor a worshipping rustic playmate. She is an intense, solitary, proud femalewho complements and reflects the mood of Krishnas passion. She the Krishnas partner in a secret and exclusive love, contrasted in the poem with the circular Rasa dance Krishna performs with the entire of cowherdesses. Krishna disappears after this dance, deserting the cowherdesses; but he stays with Radha to admire and ornament her. Her relationship with Krishna culminates in their union and mutual "victory" over each other. In Jayadevas view, the profound intimacy of Krishnas concentration on Radha, in contrast wuth the diffusion of erotic energy in his play with the cowherdesses, is the perfection of Krishnas nature."
Krishna is very complex character. In Gitagovinda, Jayadeva describes Krishna on three major levels. "Krishnas relation to all living beings is expressed in his ten incarnate forms. his personal spiritual relation to human beings is expressed through the form of flute-playing adolescent cowherd. His intense spiritual intimacy with an individual human being is expressed throught the divine sensuality of his love with Radha."
Sakhi (Radhas close friend and companion) plays important part in the plot. She goes between the parted lovers to describe the condition of each to the other. Sakhi shares Radhas feelings, takes part of mediator, and brings the lovers into reunion. The friend, the poet and the audience share the experience of secretly participating in the play of divine love.
Sometimes a recital concludes with a Sloka (prayer). The sanchari-s in a sloka should be brief. This is an item without tala and provides felief after the earlier items. It also gives the musicians a chance to use their creativity.
Almost all the items of the dance repertoire, express a pronounced rhythm and are bound by thalam. However with the piece that belongs to the class of Viruttam or Sloka is the sole exception. It is a common feature to interpret through Abhinaya the Sahitya of a Viruttam, which is not bound by a dominant rhythm, though there is a subtle and almost imperceptible rhythm underneath. A comparison can be drawn between the Alapana feature of music and the Viruttam belonging to the dance repertoire.
The meaning of the word "sloka" can be translated as "something heard", "song" or "sound". Slokas were born of the oral tradition of preservation and transmission of knowledge, very characteristic for ancient and even medieval India. A very few words are used to convey the maximum amount of information, including direct meaning, implied meaning, connotations and etc. Thus, this form of lyrics is very suitable for Bharata Natyam Abhinaya, which is symbolic, associative and suggestive as well.