There has been a great deal of discussion on this forum as to the definition of tapi tapi. Feel free to review the posts. I don't want to open a huge can of worms here, but...
The Professor told me on more than one occasion that Tapi Tapi was loosley defined as counter for counter. It is a combination of drills and concepts that function together into a simulated stick sparring situation.
It is comprised of 5 basic but distinct parts including a basic single stick siniwali pattern (including sweep stroking and punyo entering), abercidario (obstruction removal), cueridas (block check counter), trapping/dumog(grapppling) followups and striking. In a purely conceptual analysis, it teaches ranges of combat implicitly while in motion.
It is taught primarily as a drill, but in my opinion serves as a conceptual framework for exploration in this art. I have always believed, in my Modern Arnis and other training that we teach drills and explain concepts to synthesize techniques.
Despite what label we choose to call it, even in his most basic drills, Professor Presas was genius at giving us the whole of his art, but leaving it to us to explore and unpack it. Tapi Tapi is one of the many places one can begin this exploration of Modern Arnis.
Best Advise, don't get bogged down in terminology, but train and 'Find the Way'
Respectfully,
Brett