Natyashastra
त्र्यङ्गविच्छेदकं विन्द्याद्युक्तं प्रक्रीडितादिभिः । अनिष्ठुरश्लक्ष्णपदं गान्धारीजातिमाश्रितम् ॥ ३१६॥
It should be composed of three parts (tryaṅga-vicchedaka), accompanied by playful movements and the like. Its words should be neither harsh nor too smooth, and it should be based on the Gāndhārī musical mode (jāti).
english translation
tryaGgavicchedakaM vindyAdyuktaM prakrIDitAdibhiH । aniSThurazlakSNapadaM gAndhArIjAtimAzritam ॥ 316॥
hk transliteration by Sanscript