The concept of rAga padam. First I imagined how Dr HMB's valli nAyaka nI starts. From pancamam touching prati madyamam, then gaaaa.. ri sa ri effectively doing a nAyaki just like ranga naa...yakam ( there may be many other contours and anusvaras - but I am simplifying to make my argument
).Then he was not alone. sidhhi vinAyakam - at naaa.yakam does eerily similar gaaa...ri-sa,
Plot thickens only when we take into account other gandharas like antara gandhaara - raghu naayaka where naayaka is gaa..ri-sa
And boom!! suddha gandharam : https://youtu.be/8QJuImTUgjo?t=343 sEshacala naa...yakam!
And that gives an hitherto unknown , undiscovered sangati ( well may be sung by a thoughtful, deliberate , unhurried musician some place, of course with no idea of the concept of rAga padam, but wanting to take bEdaga for a slow walk!) for vallaba naayakasya - ga-ri-sa occurs in the notation at the very end after lot of contours/detours - but can be made formal by making entire naayakasya as that only!