Absolutely no case for a "post-trinity" OVK
The following "analysis" is quite unnecessary given the more erudite and detailed internal evidence cited by Shri Chitravina Ravikiran in various books, lectures and online discussions including this one. Still, for what it is worth, this is a hasty and haphazard attempt to debunk the case for a "post-trinity" OVK purely based on common sense. All of the dates I cite below are from memory (dates are my mental placeholders to place people in historical context) and may have slight errors that are irrelevant to the points made.
Tyagaraja died in 1847, MD in 1835 and SS around the same time.
So let us say the great "post-trinity" musical genius OVK lived between 1820 and 1890. Or choose something similar, say 1830 to 1900. Keep in mind that the later the date, the weaker the case as will be shown hereinunder.
First, think how unlikely that somebody who lived in this highly scrutinized period of extensive intercity travel and communication would go unnoticed. This was the Victorian era when the British empire and civil administration was firmly established in the Madras presidency.
My late father in law's grandfather Shri Sulamangalam Vaidyanatha Bhagavathar lived between 1866 and 1943 and wrote extensively on the musicians and harikatha exponents of his time. Given that the Bhagavathar was a leading Harikatha exponent of his times who conducted an annual Radha-Kalyana Uthsavams, it is absolutely inconceivable that he would not have met or talked about a contemporary who was not only an extraordinary musical genius but also a great Krishna bhakta. That too from an adjoining village which was part of an exclusive group of villages (Melattur, Sulamangalam, Oothukadu, etc..) known for the Bhagavatha mela. In fact, OVK would have been the presiding "chief" guest in the Sulamangalam Radha Kalyanams and the stories would be part of the family folklore. Oh, how I wish it were so!
The fact is, Sulamangalam Vaidyanatha Bhagavathar never mentioned OVK anywhere in his writings. As he did not Annamacharya or Arunagirinathar. Because OVK was not a contemporary or connected in anyway with his contemporaries (as in Tyagaraja was connected by way of his numerous shishyas and shishya parampara who where the Bhagavathar's conemporaries).
The post trinity period is very very close to ours and many people born in that period come tantalizingly close to our own generation. Patnam Subramania Iyer lived between 1845 and 1902 while Maha Vaidyanatha Sivan between 1844 and 1893. All this overlaps with people who lived within a hair's breadth of our own times, such as Tiger Varadachari (1875-1950), Mysore Vasudevachar (1861-1960), Harikesanallur Muthiah Bhagavathar (1870-1945). All these people had close contact with the great generation of musicians born between 1890 (ARI) and say 1916 (Alathur Sivasubramania Iyer) in many cases as their gurus. And yet none of that great generation - ARI, Musiri, Maharajapuram, Alathur, SSI, MMI - ever talked about their "gurunathars" meeting thsi great composer OVK. And yet many of them sang OVK's more well-known compositions, certainly the Tamil ones. It is inconceivable that not one of them would have mentioned something about this extraordinary vaggeyakara in some context.
The history of late 19th century and early 20th century Carnatic music is well documented and analyzed. Veena Dhanammal's (1868-1939) musical collaborations with Dharmapuri Subbarayar (mid to late 1800's), Vina Kuppaiyar (mid to late 1800's), Tiruvottiyur Tyagaiyyar (died 1920 I think) and Kanchipuram Naina Pillai (1889*-1938) are well known. What the heck, I've had the privilege of meeting the venerable T Sankaran who served for a time as Tyagaiyyar's willing errand boy. Similarly, I have had the privilege of meeting Shri M D Ramanthan, the star disciple of Tiger Varadachariar (1875 born). Shri S R Janakiraman, the living legend of musicology, was another star disciple of Tiger. If anybody want's to touch the feet of a real person who has touched the feet of Tiger Varadachari who has touched the feet of Patnam Subramania Iyer, lose no time in contriving to seek Shri SRJ's blessings. Like the famed Erdos number, SRJ is the only person living with a "Patnam number" of 2. What a privilege, huh !
Those of us born and raised in Tamil Nadu who have read and followed Carnatic music and its recent history closely have a fairly good idea of the great names associated with it, who might have met who and when and so on. Interesting tidbit: Patnam Subramania Iyer met Swami Vivekananda in 1900 at the behest of Bhaskar Sethupathi in Ramnad.
Given all of this, it is inconceivable that OVK lived anytime in the early to late 19th century.
That leaves OVK either a contemporary of the trinity or more likely...gasp...PRE-TRINITY
. Now the naysayers are free to issue a "fatwa" against me for this blasphemy
*: It is my opinion that the "official" year of birth ascribed to Naina Pillai, 1889, is wrong. He must have been born at least a decade earlier earlier. I cannot believe that he was only 23 years older than Brindamma and that he was only about 30 years old when Brindamma started her lessons with him. In those days, nobody kept any birth records.