🚀 go-pugleaf

Probably the most traditional use of a serif font as a headline over
serif text is with so-called titling fonts, which usually come in all
caps, and are carefully studied variations on a text font.   Two prime
contemporary examples of this are Zapf's Michelangelo and Sistina, which
were both designed to accompany Palatino.  Setting headlines in one of
these cap-only fonts, with generous letterspacing, is considered very
elegant.  Another one to use, in all caps, is Trajan.

The key difficulty in using a serif font with serif text is one of
generating sufficient contrast between the two.  Besides varying from
regular to bold or increasing the size, there are many other things
one can do to alter the appearance of a text font when using it as a
headline (and I'm not talking about condensing or expanding it).
Reversing into a bar, adding a drop- or drag-shadow, increasing or
decreasing the letterspacing significantly, setting in all caps,
would all serve to create contrast.  Using a font with a different
serif, such as the square-serifed Glypha or Stymie or Lubalin Graph,
over a text font with very round fillets like Times or Baskerville,
also provides tension.

Alternately, you can set headlines in a serif font and use sans serif
for text.  There is a negligible increase in eye fatigue over the long
run, but legibility is not really sacrificed.
-- 
  Peter Zelchenko  pete@speedy.acns.nwu.edu
  Typographer      pete@chinet.chi.il.us