An Opus number (Latin sing. "work", "labour", a work of art, 1695–1705), pl. opera and opuses, abbreviated, sing. Op. and pl. Opp. refers to a number generally assigned by composers to an individual composition or set of compositions on publication, to help identify their works. Opus numbers have been used inconsistently throughout history and by individual composers, and thus are not generally a good indicator of the chronological order of the compositions or the relative completeness of a given collection. Opus numbers are commonly used to organise catalogues of musical compositions. The Latin plural, opera, also denotes the opera music genre, wherein the works also are (occasionally) identified with a musical composition opus number, as in the grand opera Samson and Delilah, Op. 47, by Camille Saint-Saëns.

In the arts, opus number usually denotes a work of musical composition, a practice and usage established in the seventeenth century when composers identified their works with an opus number. In the nineteenth century, publishers usually assigned opus numbers when publishing groups of like compositions, usually in sets of three-, six-, and twelve compositions. Consequently, opus numbers are not usually in chronological order, unpublished compositions usually had no opus number, and numeration gaps and sequential duplications occurred when publishers issued contemporaneous editions of a composer’s works, as in the sets of string quartets by Joseph Haydn (1732–1809) and Ludwig van Beethoven (1770–1827); Haydn's Op. 76, the Erdödy quartets (1796–97), comprises six discrete quartets consecutively numbered Op. 76 No. 1 – Op. 76 No. 6; whilst Beethoven's Op. 59, the Rasumovsky quartets (1805–06), comprises String Quartet No. 7, String Quartet No. 8, and String Quartet No. 9.

Luciano Berio, Cavaliere di Gran Croce OMRI (October 24, 1925 – May 27, 2003) was an Italian composer. He is noted for his experimental work (in particular his 1968 composition Sinfonia for voices and orchestra and his series of numbered solo pieces titled Sequenza) and also for his pioneering work in electronic music.

Berio was born at Oneglia (now part of Imperia). He was taught the piano by his father and grandfather who were both organists. During World War II he was conscripted into the army, but on his first day he injured his hand while learning how a gun worked, and spent time in a military hospital. Following the war, Berio studied at the Milan Conservatory under Giulio Cesare Paribeni and Giorgio Federico Ghedini. He was unable to continue studying the piano because of his injured hand, so instead concentrated on composition. In 1947 came the first public performance of one of his works, a suite for piano. Berio made a living at this time accompanying singing classes, and it was in doing this that he met American mezzo-soprano Cathy Berberian, whom he married shortly after graduating (they divorced in 1964). Berio would write many pieces aimed at exploiting her very distinctive voice.

Thomas Francis "Tommy" Dorsey, Jr. (November 19, 1905 - November 26, 1956) was an American jazz trombonist, trumpeter, composer, and bandleader of the Big Band era. He was known as "The Sentimental Gentleman of Swing", due to his smooth-toned trombone playing. He was the younger brother of bandleader Jimmy Dorsey. After Dorsey broke with his brother in the mid-1930s, he led an extremely popular and highly successful band from the late 1930s into the 1950s.

Thomas Francis Dorsey, Jr. was born in Shenandoah, Pennsylvania, the second of four children born to Thomas Francis Dorsey, Sr. and Theresa (née Langton) Dorsey. The Dorsey brothers' two younger siblings were Mary and Edward (who died young). At age 15, Jimmy Dorsey recommended his brother Tommy as the replacement for Russ Morgan in the germane 1920s territory band "The Scranton Sirens." Tommy and Jimmy worked in several bands, including those of Tal Henry, Rudy Vallee, Vincent Lopez, Nathaniel Shilkret, and especially Paul Whiteman. In 1929, the Dorsey Boys had their first hit with "Coquette" for OKeh records. The Dorsey Brothers band signed with Decca records in 1934, having a hit with "I Believe In Miracles". Future bandleader Glenn Miller was a member of the Dorsey Brothers Orchestra in 1934 and 1935, composing "Annie's Cousin Fanny" and "Dese Dem Dose" both recorded for Decca for the band. Ongoing acrimony between the brothers, however, led to Tommy Dorsey's walking out to form his own band in 1935, just as the orchestra was having a hit with "Every Little Moment."

Ramsey Emmanuel Lewis, Jr. (born May 27, 1935) is an American jazz composer, pianist and radio personality. Ramsey Lewis has recorded over 80 albums and has received seven gold records and three Grammy Awards so far in his career.

Ramsey Lewis was born in Chicago, Illinois, to Ramsey Lewis, Sr. and Pauline Lewis. Lewis began taking piano lessons at the age of four. At 15 he joined his first jazz band, The Cleffs. The seven-piece group provided Lewis his first involvement with jazz; he would later join Cleffs drummer Isaac "Redd" Holt and bassist Eldee Young to form the Ramsey Lewis Trio. Lewis is a graduate of DePaul University.

The trio started as primarily a jazz unit and released their first album, Ramsey Lewis And The Gentlemen of Swing, in 1956. Following their 1965 hit "The In Crowd" (the single reached #5 on the pop charts, and the album #2) they concentrated more on pop material. Young and Holt left in 1966 to form Young-Holt Unlimited and were replaced by Cleveland Eaton and Maurice White. White left to form Earth, Wind & Fire was replaced by Morris Jennings in 1970. Later, Frankie Donaldson and Bill Dickens replaced Jennings and Eaton; Felton Crews also appeared on many 1980's releases.

Edvard Hagerup (1781–1853) was a Norwegian solicitor and politician. He was born in Kristiansand, the son of a bishop Eiler (Kongel) Hagerup b. 1718 and Edvardine Magdalene Margarethe Christie (b. 1755).

In 1801, he studied in Copenhagen with Wilhelm Frimann Koren Brodtkorp Christie (b. 1778). Both became "Stiftsamtmann", the King's representative in a county. During the formation of the Constitution of Norway signed at Constitutional Assembly on the 17th of May 1814, Christie was secretary to the delegates led by Christian Magnus Falsen and Hagerup was adviser to the Danish Prince Christian Fredrik who was present.

He was a member of the first Norwegian Parliament, in the year 1814. He was asked to accept the post of minister, but that would require him to live in Stockholm, and he abstained. At that time he worked as an assessor.

Hagerup was later appointed County Governor of Nordre Bergenhus amt (today named Sogn og Fjordane), serving from 1822 to 1831. Seated in Bergen, as Nordre Bergenhus was administrated from outside its territory, Hagerup was elected to the Norwegian Parliament from that city for the year 1824. In 1827 he was elected to the Norwegian Parliament for a third time.