Chaya nattai is a raga found to be used by Sadguru Thyagaraja only; as no other composition is seen originally set to this raga. So the Thyagaraja krithi, “Idi Samaymura inakula thilaka”, still holds the Eka-krithi status.
The raga Chaya nattai is a janya of the mela (34) ragam Vagadeeswari; losing Chathusruthi Dhaivatham (D2) and Kaishiki Nishadam (N2) in the arohanam and Anthara Gandharam (G3) in the avarohanam, there are slight vakra prayogas in both directions; so that the ragaswaroopam will be:
S R3 G3 M1 P M1 P S // S N2 D2 N2 P M1 R3 S
‘Ragapravaham’ by D.Pattammal shows another specification under the same mela, but without the vakra in arohanam, as:
S R3 G3 M1 P S // S N2 D2 N2 P M1 R3 S
(This is the type which is explained by Chitraveena Sri. N.Ravikiran; can be heard in this link):
In the Krithi, ‘idi samayamurA’, Saint Thyagaraja asks Lord to keep His word of protecting him.
idi samayamurA inakula tilaka
vidaLita kali durmada gajagamana modaTa balkinadi nijamuga jEya
kali puruSuDu nATakamunu gaTTa dalacinADu shrI tyAgarAjanuta khala matamulane yAgamulaku mEkaluga narula jEsi nI dayajUDa”
“O Pride of Solar dynasty! O Lord who rent asunder the arrogance of kali purusha! O Lord with elephant-like gait! O Lord praised by this tyAgarAja!
Now is the time to fulfill what you said earlier.
kali purusha is contemplating to enact a drama by making men as (sacrificial) goats for the sacrificial oblations called base sects.
Now is the time to show Your mercy”.