A music conductor guides an orchestra through the sheet music.
Nineteenth century orchestras performed without a conductor, and small orchestras to this day rehearse without one, as well. However, because of the gradually increased size of orchestras, musicians became dependent on conductors. Even though a score is like a road map, orchestras still need conductors to guide them through this complicated map and its terrain.
Interpretation
Before the orchestra performs a concert live, the conductor looks over the entire piece. Memorizing all of the parts, the conductor learns where each low and high point is located for each instrument. As a result of his hard work, the conductor wants the audience to be intrigued, which can happen through his interpretation. Needless to say, each interpretation is different from the next. In fact, Tony Macaluso, author of Sounds of Chicago's Lakefront: A Celebration of the Grant Park Music Festival, states that the same piece performed by the same orchestra but with two different conductors can sound dramatically different.
Rehearsal
After reviewing the composition beforehand, the conductor hands his interpretation to the performers. When they begin to rehearse together, the conductor shows them how he wants them to perform. When the musical piece says "crescendo," the conductor decides how quickly the orchestra reaches its high point and where that high point is.
Friendly Reminders
During a concert, not all instruments play at the same time. Thus, performers take breaks and wait to start playing their instrument again. The conductor gently reminds each performer that his break will soon end. He usually does this through a subtle wink or a nod. Without him, the performer could forget or start playing at the wrong time.
Concert Tempos
While performing, orchestras can get easily carried away. Whether playing too fast, too slow, too gently or too roughly, the orchestra needs direction during the performance. The conductor acts like the director of a film. Through his gestures, he tells the musicians what to do. If the string instruments are playing too aggressively, he informs them to play softer and with less gusto.
