sentences:  The collections of suitably modified richa-s are known as Gāna-grantha.These are the true Sāma.Sāma created on richa-s of Poorvārchika are called Grāma-gāna,ग्रामगान् Grāmegeya-gāna, ग्रामगेयोगान् Prakriti-gāna प्रकृतिगान or Veya-gāna वेयगान्.