To answer that question, here is early music specialist Frederick Jodry, the Director of Choral Activities at Brown University, the founder and director of the Renaissance vocal ensemble Schola Cantorum of Boston, and one of the founders of the Providence Baroque Orchestra.
When performing 18th-century oratorios and concertos, over the past 50 years or so it has become somewhat common to try to recreate the sounds and colors that the composers would recognize. When playing Bach and Handel, for example, one tries to recreate some of the musical details that give music its distinctive colors and sounds. In general, the design of instruments have evolved over the past 200 years, largely to make the orchestral sounds louder to fill ever bigger halls. But what musical ideas have been lost in doing so?
An 18th-century violin has the same body as a modern violin, and indeed, we value the 17th-century violin makers very highly—Stradivarius and Amati, for example. But over time, most violins have been altered by changing the angle of the neck, using a higher bridge, and installing a longer fingerboard. After about 1900, steel strings became the norm. The design of bows has also changed to larger, heavier bows. Eighteenth century string instruments were strung largely with natural animal gut and were played with a lighter and more agile bow.
We find the use of historical instruments adds considerably to performances, resulting in a more transparent tone, a clearer sense of articulation, and often a different balance between the winds and strings. Baroque music is usually played at A=415 today (rather than the modern standard of A=440), a half step lower, and this detail also influences how the string instruments respond. When the violins are strung in gut, with a lower Baroque bridge, and are under less physical tension because of the lower pitch, the tone takes on a new sheen.
Baroque wind instruments are even more radically different from their modern cousins. Flutes and oboes have much simpler technology, usually only one or two keys, rather than the serious dental work of the levers and keys on modern woodwinds.The tone of the wooden flutes is softer and sweeter, the oboes perhaps more plangent, and both instruments blend with period strings more readily. The trumpets are also simpler, being played without valves, and add considerable luster and volume to the orchestral tutti.
We hope you enjoy hearing the sounds of the period instruments, and the marvelous way they support and blend with voices.
--L. F. Jodry V