I want to know the answer to the following question:
Where can a remnant of improvisation tradition be found?
All the background I'm provided with is that "Improvisation is also an important aspect in authentic performances of operas of Baroque era and of bel canto (especially operas of Vincenzo Bellini), and is best exemplified by the da capo aria, a form by which famous singers typically perform variations of the thematic matter of the aria in the recapitulation section ('B section' / the 'da capo' part).". Is that enough to answer the question?
Answer: no