A string quartet is a group of four musicians who perform a composition with four written parts. Continuing the "four" theme, a string quartet comprises four instruments. Like a modern rock band, a professional string quartet will typically stay together and tour together, playing for listening audiences in small concert halls and auditoriums. Famous string quartets include the Hungarian Quartet, Amadeus Quartet, Alban Berg Quartet and Italian Quartet.
In the second half of the 18th century, the demand for daily musical entertainment increased, creating a need for small musical ensembles. The emergence of chamber music created the demand for the string quartet, as chamber music was a four-movement work meant for a small room or chamber. The string quartet developed as two violins and a viola for the soprano alto and tenor voices, and a cello for the bass or low end, creating melodies that were “more like a musical conversation in which everyone has something to say,” according to the Avoca String Quartet.
The violin is a small four-stringed instrument that you hold under the chin and play with a bow or pluck with your fingers. The strings stretch from the tailpiece across the bridge to the tuning pegs. A string quartet uses two violins, and they are the smallest instruments in the quartet, offering the highest voice. The rich and soaring sound the violin produces allows melodies and harmonies to stand out. Players implement musical techniques such as vibrato, tremolo and pizzicato to create a rich musical voice.
The viola is slightly larger than the violin, with strings that are tuned five notes lower. Violas offer a unique voice in the string quartet, providing a rich dark tone, which is in direct contrast to the bright tone of the violin. A viola can play notes that are almost as high as a violin; however, these notes will not have the same penetrating tone, making for a more distinct voice in the ensemble.
Adding the lowest voice to the string quartet, the cello provides a smooth and rich sound. Cellos are twice as big as the viola or violin, with a thick body and thick strings that are bowed to produce deep low notes. Traditionally, the cello was held between the knees; however, at the end of the 20th century, a spike was added to the cello, allowing it to stand on the floor. The cello produces the bass voice in the string quartet.