What is usually called just "string instruments" in a symphony orchestra are the bowed string instruments developed from mainly the viola da braccio (arm viol) family. The viola is the original form of these instruments complemented by the violin (the small viola) and the violoncello (the small big viola). The fourth member of the string section is the contrabass which has its origins in the viola da gamba (knee viol) family; this is visible for example in its sloping shoulders and in its deeper body. The contrabass also uses the viola da gamba tuning of fourths instead of the viola da braccio's fifths. All these string instruments have 4 strings with the exception of the contrabass that may have five (also a similarity to the viola da gambas that usually had 6 strings).
Beside being played with a bow (arco) these instruments can also be plucked (pizzicato). The bow playing on its own provide for many different timbres and expression possibilities. In modern compositions additional playing techniques, often with percussive methods, are sometimes employed. The string instruments are able to play two notes at the same time, and sometimes even three, when using the bow; using pizzicato it is possible to play all four strings at the same time.
In the modern symphony orchestra the strings are divided into five parts.
Violoncellos, or simply Cellos
Contrabasses, or simply Basses
Each of these groups vary in size, and can be proportionally smaller or larger depending on the piece of music being played, according to the composer's intent. For an average orchestra, the numbers are considered normal when as follows:
1st Violins = 16 players
2nd Violins = 14 players
Violas = 12 players
Cellos = 10 players
Basses = 8 players
With the string parts weighted as described, a composer or orchestrator can assume balance at consistent volume levels, as a starting point.
Contributed by Magnus Johansson.