RILM abstract: "From the 17th to the early 18th c., timpani performance practice was determined by stock formulas, some of which are seen in Bach's and Handel's orchestral writing. Characteristic written-out patterns only came into use in the late 18th c. In the 19th c., rapid changes of pitch became a challenge, and hand screws and mechanical linkages with tuning levers gave way to the modern pedal timpani. The modern era featured the exploitation of various and unusual tone colors and effects, such as glissando passages, stepwise ascending and descending passages, hitting the center of the drum, using different kinds of mallets in each hand, playing with drum sticks or wire brushes, and even placing cymbals on the drum heads. In the past 300 years, the size of the timpani has changed as well, from 18-20 inches in the 17th c. to 21-32 inches in the 20th c."
Bowles, Edmund Addison
"The Timpani and Their Performance (Fifteenth to Twentieth Centuries): an Overview,"
Performance Practice Review:
2, Article 4.
Available at: http://scholarship.claremont.edu/ppr/vol10/iss2/4