A string orchestra is understood as an orchestra composed solely of certain instruments of the string family. These instruments are the violin, the viola, the violoncello, the double bass (sometimes considered an anomaly because of its resemblance to the viol family), the piano, the harp, and sometimes percussion. String orchestras can be of chamber orchestra size ranging from between 12 and 21 musicians (6,5,4,4,2 = 21) sometimes performing without a conductor, or consist of the entire string section of a large symphony orchestra which could have 60 musicians (16,14,12,10,8 = 60). A twentieth century development has been the reappearance, minus continuo, of the concerto grosso pitting of soloists against the full ensemble.

Repertoire

The repertoire is graced with several works by Mozart (including Eine kleine Nachtmusik) and Haydn which dispense with the baroque basso continuo. Some of these works are problematic when it comes to deciding whether they are for orchestra or string quartet. Particularly in Haydn's early works it is argued that the inversions of harmony from the occasional crossings of the bass and viola line imply a double bass; the question is not settled, however.

Important 20th century works have been written for string orchestra by Béla Bartók (Divertimento), Stravinsky (Apollon Musagète), Witold Lutosławski (Funeral Music) (Muzyka zalobna, 1958), Benjamin Britten (Simple Symphony), and Malcolm Williamson (Symphony No. 7). Sir Michael Tippett wrote a Concerto for Double String Orchestra and Ralph Vaughan Williams wrote a Partita for Double String Orchestra. Composers that have written a "Serenade for Strings" for string orchestra include Tchaikovsky, Antonín Dvořák, Josef Suk and Edward Elgar. Mendelssohn also wrote a number of symphonies for string orchestra.

Sometimes works originally written for string quartet are arranged for string orchestra. Samuel Barber's Adagio for Strings, Alban Berg's 3 Pieces from his Lyric Suite, Arnold Schoenberg's Second String Quartet and the sextet Verklärte Nacht, John Corigliano's Second String Quartet and Jean Sibelius's Andante Festivo for string orchestra are examples, though a timpani is also added in the Sibelius piece. The work Shaker Loops written in 1978 for septet then arranged in 1983 for string orchestra by the American composer John Coolidge Adams has become a popular addition to the repertoire in recent times. Graham Waterhouse composed several works for string orchestra (Sinfonietta), also in combination with contrasting sounds as Great Highland Bagpipe (Chieftain's Salute).

Other works for string orchestra

• Giovanni Albini - Una teoria della prossimità (2006)

• Samuel Barber - Adagio for Strings

• Leonard Bernstein - Serenade for Solo Violin, Strings, Harp and Percussion

• Ernest Bloch - Concerto Grosso No. 2

• Carlos Chávez - Symphony No. 5

• Christopher Culpo - 3 visages

• Edward Elgar - Introduction and Allegro for Strings (1904-1905)

• Edvard Grieg - Holberg Suite (originally written for piano then arranged for string orchestra)

• Gustav Holst - St Paul's Suite

• David Johnstone - more than 20 published works for string orchestra

• Nigel Keay - Serenade for Strings

• Aulis Sallinen - Aspects of the Funeral March of Hintriki Peltoniemi (originally written for string quartet then arranged for string orchestra)

• William Schuman - Symphony No. 5

• Rodion Shchedrin - Carmen Ballet

• Richard Strauss - Metamorphosen for 23 solo strings

• Igor Stravinsky - Concerto in D

• Dimitri Tchesnokov - Réminiscence d'après la symphonie pour cordes

• Robin Toan - dans la nuit (2006)

• Ralph Vaughan Williams - Fantasia on a theme by Thomas Tallis, Five Variants on Dives and Lazarus, Concerto Grosso

• Anthony Watson - Prelude and Allegro for Strings (1960)

• Takashi Yoshimatsu - Threnody to Toki for Piano and String Orchestra (1980)

• Malcolm Williamson - Epitaphs for Edith Sitwell (1966/72), Ode for Queen Elizabeth (1980), Lento for Strings (1985)

• Djuro Zivkovic - Serenade (2002)