In kaiśikī, ṛṣabha is sparse and may be omitted to derive hexatonic/pentatonic forms; tānas can be built without ṛṣabha
Body (pseudocode)
FUNCTION derive_by_rsabha_omission(jati):
IF jati == 'kaisiki':
omit({rsabha}) -> hexatonic
omit({rsabha, dhaivata}) -> pentatonic
FOR tana IN tanas:
ALLOW construction WITHOUT rsabha
Inputs / output
jati_or_tana
—
→ derived_form
Evidence (2)
p. vol_II_p040 · #467« The hexatonic and pentatonic forms are known to come into being with the omission of ṛṣabha and ṛṣabha-dhaivata. »