Natyashastra
भाण्डवाद्यकृते चैव तथा गानकृतेऽपि च । एका तु प्रथमं योज्या द्वे द्वितीयं तथैव च ॥ २८६॥
The same applies to both drum music and singing: one dancer should be assigned to the first, two to the second, and similarly for the others.
english translation
bhANDavAdyakRte caiva tathA gAnakRte'pi ca । ekA tu prathamaM yojyA dve dvitIyaM tathaiva ca ॥ 286॥
hk transliteration by Sanscript