Natyashastra
तयोरागमने कार्यं गानं नर्कुटकं बुधैः । तथा च भारतीभेदे त्रिगतं सम्प्रयोजयेत् ॥ १३३॥
Their arrival should be accompanied by singing and the Narkuṭaka, as understood by the wise. Similarly, in the variation of the Bhāratī style, the Trigata should be employed.
english translation
tayorAgamane kAryaM gAnaM narkuTakaM budhaiH । tathA ca bhAratIbhede trigataM samprayojayet ॥ 133॥
hk transliteration by Sanscript