Natyashastra
वितस्तालिप्तमार्गेण सैन्धवं वाद्यमिष्यते । न पाठ्यं स्वल्पमप्यत्र प्रकुर्वीत विचक्षणः ॥ ३२१॥
The Saindhava should be performed with instrumental accompaniment following the Vitastāliptamārga (a specific rhythmic pattern). A wise performer should not introduce even a small amount of spoken or recited text in it.
english translation
vitastAliptamArgeNa saindhavaM vAdyamiSyate । na pAThyaM svalpamapyatra prakurvIta vicakSaNaH ॥ 321॥
hk transliteration by Sanscript