The most famous classical piece with a continuous drumbeat is surely
Ravel's "Bolero." Another one that has a long drum ostinato through much
of it's length is the Shostakovich 7th symphony (which, unlike the Ravel,
is a colossal bore).  The first movement of Nielsen's 5th symphony also
features an often obsessive drum pattern.  Often conductors during the
baroque era would strike a post against the floor to mark their
meters--perhaps these could count as "drum beats." A really neat percussion
ensemble work to check out is Henry Cowell's "Ostinato Pianissimo."

Aaron J. Rabushka
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