What is an orchestra?

At a high level, despite all those players on stage, there are only four parts to an orchestra. This is because all the instruments fall into one of four orchestral "sections": Woodwinds, Brass, Percussion and Strings. If you were to look at a conductor's score (the printed music he has on the stand in front of him) you would see those very same four sections arranged in that order from the top of the page to the bottom.

Woodwinds ("The Winds")



Woodwinds are mostly comprised of instruments that make sounds when a player uses his/her lips to vibrate a small piece of wood, called a reed. The rest of the instrument amplifies the sound of the vibration, and provides mechanisms (keys played by fingers) to change the amplification by changing the airflow through the instrument. The flute and piccolo do not have reeds, but rather a small air hole over which a player blows.

The woodwinds range in timbre (that means the color of the sound, or how the sound, er... sounds) from shrill to sonorous; they have a generally mellow sound. From those that sound the highest (birdlike!) to lowest (like grandpa with a deep cold!) they are: the piccolo, the flute, the oboe, the clarinet, the bassoon, and the contrabassoon. When you hear very fast, high-pitch runs, you are quite likely hearing a piccolo or flute, though the flute also has a very pleasing, if less frequently used, lower register. There are others that are slight variations of these, such as the alto flute, English horn, and bass clarinet, but they are less common. When you see these other instruments, they look like larger versions of their counterparts, and there is typically only one of them.

Brass



Brass instruments are also played by a player's lips, but instead of vibrating a reed, the player vibrates his/her own lips on a metal mouthpiece, and employs the horn's tubes to change way the airflow is amplified into sound. The player uses pistons to change the way air flows through the tubes of the instrument -- except for the trombone, which has a long slide that a player moves to make the tube longer or shorter. Brass instruments are the shiny golden or silver ones with loud, heroic tones; from highest in pitch to lowest, they are: trumpet, trombone, and tuba. The horn, aka French Horn, is also a brass instrument, but it has a slightly mellower sound and can play very well with woodwinds as well as brass. If you remember Luke Skywalker's theme from Star Wars, you remember the sound of the horn.

Percussion



Percussion instrument make sounds by causing vibrations as well, but instead of a player using his lips (although that would be interesting!), the player bangs on the instrument to cause vibrations. These instruments include an enormous variety of instruments that are grouped into two subcategories: pitched percussion and non-pitched percussion. The difference is that the former percussion instruments make actual notes when struck, while the latter make sounds that can't quite be considered notes. The most common pitched percussion instruments you will see are the large drums called timpani drums: there are usually a few of these, as they are tuned to sound certain notes (so you need more than one to make more than one single pitch). Non-pitched percussion includes instruments like snare drums and tambourines. Other percussion instruments include all of those played with mallets, such as vibraphone, xylophone, glockenspiel, windchimes, gongs, and so forth.

Even a piano is occasionally considered a percussion instrument in orchestral terms -- if you think about it, the vibration is caused by striking keys with your fingers, which in turn cause hammers in the piano to strike strings to make sounds. More often, though, piano and celesta (which looks like narrow piano) are treated as their own special section.

Strings



String instruments comprise the largest section of the orchestra, and they have five subcategories: first violins (the largest section in the orchestra), second violins (they usually play a part slightly lower in pitch than the first violins), the viola (it looks like a larger version of a violin, and has a lower sound), cello (so large it has to sit on the ground, it has a marvelous romantic sound), and bass or contrabass (which looks like a large cello, so large that its tuning pegs stand taller than most adults!). The strings all make music by vibrating the strings of the instrument, amplified by the wood of which the instrument is constructed.

Strings have the ability to play forever, or until the players collapse in exhaustion, since they make sound whenever a bow is drawn across the instruments' four strings. When you hear a steady, drawn out (sustained) set of notes, or a trill of notes in moments of tension, you are very likely hearing the string section. Commercial music these days makes frequent use of pizzicato, which is a technique by which the strings are plucked (like a guitar) instead of bowed. The resulting sound is a short, almost percussive tone.

Whether the figure standing on the podium in front of the orchestra is a man, woman, child, or robot, one thing is absolute: this is the boss. In orchestral music there is no improvising, and there is a strictly-obeyed hierarchy, else music turns to a lot of noise.

The conductor sets the tempo of the performance by beating out the current rhythm with one (and occasionally both) hands. If the conductor uses a baton -- a white stick that is easier to see than bare hands -- then that baton hand will beat out the tempo. The conductor makes different movements and shapes based on the timing of the music, and can slow the orchestra or speed it up in this way. The written music will give general directions that essentially say, "speed up here," or "slow down here," but the conductor determines how "fast" fast is and how "slow" slow is.

The conductor typically uses his other hand to signal changes in "dynamics," which is a word that refers to how loudly or softly a player or section is playing. The conductor makes very expressive gestures to the sections to say, "quieter!" or "louder!" or "more power!" or "more expressive, give me romance!" When a conductor sneezes, chaos ensues.

Seriously, a conductor is a lot like a live DJ or producer, and is credited for creating a specific interpretation of a composer's piece similarly to the way a producer or DJ might be credited for creating a cover of a famous song.

Orchestras sit in a semi-circle facing the conductor. Here's where each of these sections sit relative to a conductor who is facing the orchestra (back to audience, so the conductor's left is the audience's left):



The strings sit in front, the woodwinds and brass sit in the middle but behind the strings, and the percussion is arrayed along the semi-circle at the very rear of the orchestra.

First violins to the far left; there are typically 16 players in this section. There are many because it takes many voices to bring the entire section up to a suitable volume and timbre for most orchestral pieces. The violinist to the farthest left is called the 'concertmaster' and is the leader of the string section. This person will often work out the bowings (whether certain notes are played on up-bows or down-bows) for the rest of the section, and acts as the conductor's lieutenant.

Second violins also sit on the left but starting closer to the middle of the circle and spreading out behind the first violins, and there are around 14 players in this section. There are around 12 viola players, and they sit toward the right side of the conductor, next to the second violins, to the right of the center. There may be 10 cellos, and they sit on the far right side of the conductor, opposite the first violins. The basses sit on the right just behind the cellos, and there may be 8 of them in a full modern orchestra. The harpist will sit on the left in the rear, and if there is a piano or celesta they will be next to the harpist.

The other sections are all much smaller, because they don't need the same number of players to reach suitable volume and tone, owing to their frequency ranges and timbre.

There is often a single piccolo player in the woodwinds, and this player will sit with the flute section. This player typically doubles the flute part, and is often a flutist who picks up the piccolo when needed. There are often 3-4 flutes who sit in the middle, behind the array of strings; just next to them toward the conductor's right sit three oboes; behind the flutes sit three clarinets, and behind the oboes sit three bassoons. When there are other instruments, there is usually only one of them: English horn, Bass clarinet, and Contrabassoon, and they are played by one of the players in the appropriate section (for example, a clarinet player may put down his clarinet and play bass clarinet, leaving 2 clarinet players to stick with the clarinet part).

The brass section tends to be the one that casual listeners remember the most after a performance, owing to their dominating sound. Yet they often have the longest sections of rest in orchestral pieces. They are comprised of four horns (most musicians don't use the term 'French horns' and instead call them simply 'horns'), which are typically split between two which play low parts and two which specialize in the difficult to reach higher passages; the horns blend so well with woodwinds that they typically sit right behind the winds section, smack dab in the middle of the orchestra. The rest of the brass tends to be slightly farther back and to the right: 3-4 trumpets sitting in front of 3-4 trombones, and a tuba next to the trombones.

The percussion instruments will be arrayed in the very rear of the orchestra or spilling out on either side depending on the stage, and often consist of a few players who move back and forth between multiple instruments. There can be any number of these characters, but they seldom if ever outnumber any of the other sections (a little percussion goes a long way!).