A string quartet is a type of musical piece or a group of four musicians who play it. Many composers from the mid-1700s onward wrote string quartets. The group includes two violinists, one violist, and one cellist.

The string quartet was developed into its modern form by the Austrian composer Joseph Haydn. His works in the 1750s helped establish the quartet as a group of four musicians who work together as equal partners. Since then, the string quartet has been seen as a respected musical form. Writing for four instruments with similar characteristics challenges composers to create music that is both balanced and complex. String quartet composition was especially popular during the Classical era, with composers like Mozart, Beethoven, and Schubert writing many examples. Later, Romantic and early 20th-century composers, including Mendelssohn, Schumann, Brahms, Dvořák, Janáček, and Debussy, also composed string quartets. There was a short period of fewer compositions in the late 1800s, but the form became popular again in the 20th century. Composers such as those in the Second Viennese School, Bartók, Shostakovich, Babbitt, and Carter created highly respected string quartets. Today, the string quartet remains an important and refined musical form.

The standard structure of a string quartet, as established during the Classical era, includes four movements. The first movement is usually in sonata form and is played in a fast tempo (allegro) in the main key. A slow movement follows, often in a related key, followed by a minuet and trio. The final movement is often in rondo form or sonata rondo form, returning to the main key.

Some string quartet groups perform together for many years and become well-known, similar to a solo musician or an orchestra.

History and development

The early history of the string quartet shows how the genre developed. Joseph Haydn, an Austrian composer, played a major role in this process. Before Haydn, composers like Georg Christoph Wagenseil and Ignaz Holzbauer in Vienna wrote music for two violins, viola, and cello. There was also a tradition of playing orchestral music with one instrument per part. David Wyn Jones, a British music expert, notes that four musicians often played works written for string orchestra, such as divertimenti and serenades. These pieces did not include a fifth instrument, the contrabass, until the 19th century. However, these earlier composers did not focus on developing the string quartet as a unique form of music.

The string quartet’s origins can be traced back to the Baroque trio sonata, which included two solo instruments and a continuo section with a bass instrument (like the cello) and a keyboard. An early example is a four-part sonata by the Italian composer Gregorio Allegri, which may have been an important model. By the early 1700s, composers began adding a third soloist and often removed the keyboard part, letting the cello handle the bass line alone. This led to works like Alessandro Scarlatti’s "Sonata à Quattro per due Violini, Viola, e Violoncello senza Cembalo," which marked a natural step in the evolution of the quartet.

Musicologist Hartmut Schick suggests that Franz Xaver Richter may have created the "classical" string quartet around 1757. However, most experts agree that Haydn shaped the genre into its modern form. Unlike the trio sonata, the string quartet did not have a clear place in musical traditions for many years. Haydn’s earliest quartets were not written with a clear plan but more by chance.

In the 1750s, when Haydn was still teaching and playing violin in Vienna, he sometimes visited the nearby castle of Karl Joseph Weber, an Austrian nobleman who loved music. There, Haydn played chamber music with a group that included a steward, a priest, and a local cellist. When the Baron asked for new music, Haydn began writing his first string quartets. It is unclear if these early works were later published as his Op. 1 and 2, but they likely shared similar features.

Haydn’s early biographer, Georg August Griesinger, wrote that Haydn composed nine more quartets around this time. These were published as Op. 1 and 2. One quartet remained unpublished, and some early "quartets" were actually symphonies missing wind instruments. These works had five movements: fast, minuet and trio, slow, minuet and trio, and fast finale. Ludwig Finscher notes that they reflected the Austrian divertimento tradition.

After these early works, Haydn did not return to the string quartet for several years. During this time, he became Kapellmeister to the Esterházy princes, composing many symphonies and trios for violin, viola, and the baryton (a string instrument played by Prince Nikolaus Esterházy). These experiences helped him develop the more advanced style seen in his 18 works published in the 1770s as Opp. 9, 17, and 20. These quartets followed a standard four-movement structure, with balanced first movements and more equal interaction between instruments. The Op. 20 set, in particular, became a major milestone in the history of the string quartet. These works influenced composers like the teenage Mozart, who later imitated their features, including complex fugues in the finales.

After Op. 20, Haydn’s string quartets did not show the same major changes, but this was not due to a lack of creativity. As Donald Tovey wrote, "with Op. 20, the historical development of Haydn’s quartets reaches its goal; further progress is not progress in any historical sense, but simply the difference between one masterpiece and the next."

Musicologist Roger Hickman disagrees with the idea that Haydn "invented" the string quartet. He points out that by the late 1760s, other composers were writing quartets with modern features—two violins, viola, cello, solo passages, and no basso continuo. He argues that Haydn’s earlier quartets did not meet these standards, suggesting that Haydn was not the genre’s true creator but its "father" in the Classical style.

Cliff Eisen describes Haydn’s Op. 20 quartets as key moments in the quartet’s early history. These works used varied textures, unusual rhythms, and dramatic gestures. They established the four-movement structure, expanded the genre’s scope, and raised its artistic ambitions.

By 1801, Haydn’s string quartets were already considered classics that defined the genre. Ignaz Pleyel published a complete series of quartets in Paris that year, and he also created miniature scores for audiences, showing the quartet’s growing role in public performances. Since Haydn’s time, the string quartet has been a respected form, partly because it requires more skill to write for four equal instruments without relying on orchestral color.

During the Classical era, composers like Mozart, Beethoven, and Schubert wrote many quartets. Beethoven, in particular, pushed the genre forward with experimental and dynamic works, especially in his later quartets from the 1820s. His innovations continue to inspire musicians today.

String quartets of the classical period

Quartets from the classical period usually had four parts, similar to those in a large musical piece called a symphony. The slow part and the third part could change places. In six quartets written by Mozart for Haydn, three had a minuet followed by a slow part, and three had the slow part before the minuet.

By the time of Beethoven's later quartets, there were already many changes to this structure. Although some composers still used the old way, many in the twentieth century stopped using it. Bartók's fourth and fifth string quartets, written in the 1930s, had five parts, arranged in a balanced way around the middle part. Shostakovich's final quartet, written in the 1970s, had six slow parts.

Variations of string quartet

Many other chamber groups are based on the string quartet:

• The string quintet includes a string quartet plus one more string instrument. Mozart used two violas in his string quintets, while Schubert used two cellos. Boccherini wrote some quintets with a double bass as the fifth instrument. Most of Boccherini’s string quintets have two violins, one viola, and two cellos. Ethel Smyth also wrote a string quintet with two cellos.
• The string trio has one violin, one viola, and one cello.
• The piano trio includes a piano, a violin, and a cello.
• The piano quintet is a string quartet with a piano added.
• The piano quartet is a string quartet with one violin replaced by a piano.
• The clarinet quintet is a string quartet with a clarinet added, such as those written by Mozart and Brahms.
• The string sextet has two violins, two violas, and two cellos. Brahms wrote two string sextets.

Larger groups include the String Octet by Mendelssohn, which has the same number of instruments as two string quartets. Schoenberg added a soprano singer in the final two movements of his second string quartet, written in 1908. Other composers, such as Milhaud, Ginastera, Ferneyhough, Davies, and İlhan Mimaroğlu, also included a voice in their works. A different version of the string quartet is the electric string quartet, where players use electric instruments.

Notable string quartets

Important works for string quartet include:

• Joseph Haydn's 68 string quartets, especially Op. 20, Op. 33, Op. 76, Op. 64, No. 5 ("The Lark"), and the string quartet version of "The Seven Last Words of Our Saviour On the Cross" (Op. 51)
• Wolfgang Amadeus Mozart's 23 string quartets, especially the set of six dedicated to Haydn, including K. 465 ("Dissonance")
• Ludwig van Beethoven's 16 string quartets, especially the five "middle" quartets Op. 59 nos 1–3 ("Rasumovsky"), Op. 74, and Op. 95; as well as the five late quartets, Opp. 127, 130, 131, 132, and 135, plus the Grosse Fuge, Op. 133, the original final movement of Op. 130
• Franz Schubert's 15 string quartets, especially the String Quartet No. 12 in C minor ("Quartettsatz"), String Quartet No. 13 in A minor ("Rosamunde"), String Quartet No. 14 in D minor ("Death and the Maiden"), and String Quartet No. 15 in G major
• Felix Mendelssohn's 6 numbered string quartets, especially the String Quartet No. 2 (early example of cyclic form) and the early unnumbered string quartet in E♭ major
• Robert Schumann's three string quartets, Op. 41, in A minor, F major, and A major (1842)
• Johannes Brahms's three string quartets, Op. 51 No. 1 (in C minor), Op. 51 No. 2 (in A minor), and Op. 67 (in B♭ major)
• Giuseppe Verdi's String Quartet in E minor (1873)
• Pyotr Ilyich Tchaikovsky's three string quartets (1871, 1873/74, 1876)
• Anton Arensky's Second String Quartet in A minor, unusually written for violin, viola, and two cellos (1894)
• Antonín Dvořák's String Quartets Nos. 9–14, especially String Quartet No. 12 in F major, "American"; also No. 3 is an exceptionally long quartet (lasting 65 minutes)
• Bedřich Smetana's two quartets, especially String Quartet No. 1 in E minor, "From my Life" (1876), considered the first piece of chamber programme music
• César Franck's String Quartet in D major (1889–1890)
• Claude Debussy's String Quartet in G minor, Op. 10 (1893)
• Maurice Ravel's String Quartet, in F major (1903)
• Max Reger's six string quartets (including an early unnumbered one), especially long Quartet No. 3 in D minor, Op. 74 (1903–04), Quartet No. 4 in E♭ major, Op. 109 (1909), and the last, Quartet No. 5 in F♯ minor, Op. 121 (1911)
• Jean Sibelius's String Quartet in D minor, Op. 56, Voces intimae (1909)
• Alexander Zemlinsky's Second String Quartet, Op. 15 (1913–15)
• Edward Elgar’s String Quartet op. 83 in E minor (1918)
• Gabriel Fauré’s String Quartet op. 121 in E minor (1924), the composer’s last work
• Leoš Janáček's two string quartets, String Quartet No. 1, "Kreutzer Sonata" (1923), inspired by Leo Tolstoy's novel The Kreutzer Sonata, itself named after Beethoven's Kreutzer Sonata; and his second string quartet, Intimate Letters (1928)
• Béla Bartók's six string quartets (1909, 1915–17, 1926, 1927, 1934, 1939)
• Arnold Schoenberg's four string quartets – No. 1 Op. 7 (1904–05), No. 2 Op. 10 (1907–08, noteworthy for its first ever inclusion of the human voice in a string quartet), No. 3 Op. 30 (1927), and No. 4 Op. 37 (1936)
• Alban Berg's String Quartet, Op. 3 (1910) and Lyric Suite (1925–26), later adapted for string orchestra
• Anton Webern's Five Movements, Op. 5 (1909), Six Bagatelles, Op. 9 (1913), and Quartet, Op. 28 (1937–38)
• Darius Milhaud's set of 18 string quartets written between 1912 and 1950, especially nos. 14 and 15 op. 291 (1948–49), which can be played simultaneously as a string octet
• Heitor Villa-Lobos's 17 string quartets (1915–57), especially the Fifth ("Popular"), Sixth ("Brazilian"), and Seventeenth String Quartets
• Ruth Crawford-Seeger's string quartet (1931)
• Alois Hába's 16 string quartets (1919–67), some of them in quarter-tone tuning, the last in fifth-tone tuning
• Dmitri Shostakovich's 15 string quartets, especially the No. 8 in C minor, Op. 110 (1960), and No. 15 Op. 144 (1974) in six Adagio movements
• John Cage's String Quartet in Four Parts (1950)
• Elliott Carter's five string quartets (1951, 1959,

String quartets (ensembles)

While some individual string players form temporary string quartets, others remain in groups for many years. These groups may be named after the first violinist, such as the Takács Quartet, a composer, like the Borodin Quartet, or a place, such as the Budapest Quartet. Even when established quartets change members over time, they often keep their original name.