In vocal jazz, scat singing is vocal improvisation with wordless vocables, nonsense syllables or without words at all. Scat singing gives singers the ability to sing improvised melodies and rhythms, to create the equivalent of an instrumental solo using their voice.

Though scat singing is improvised, the melodic lines are often variations on scale and arpeggio fragments, stock patterns and riffs, as is the case with instrumental improvisers as well as singers. As well, scatting usually incorporates musical structure. All of Ella Fitzgerald's scat performances of "How High the Moon", for instance, use the same tempo, begin with a chorus of a straight reading of the lyric, move to a "specialty chorus" introducing the scat chorus, and then the scat itself.Will Friedwald has compared Ella Fitzgerald to Chuck Jones directing his Roadrunner cartoon—each uses predetermined formulas in innovative ways. Among the greatest exponents of the scat style was Mel Tormé, a child prodigy drummer who went on to become one of the most influential jazz performers of the 20th century. Tormé's effortless scatting was built on his outstanding big-band arrangement and multi-instrumentalist skills.

Ella Jane Fitzgerald (April 25, 1917 – June 15, 1996), also known as the "First Lady of Song", "Queen of Jazz", and "Lady Ella", was an American jazz and song vocalist. With a vocal range spanning three octaves (D♭3 to D♭6), she was noted for her purity of tone, impeccable diction, phrasing and intonation, and a "horn-like" improvisational ability, particularly in her scat singing.

Fitzgerald was a notable interpreter of the Great American Songbook. Over the course of her 59-year recording career, she was the winner of 13 Grammy Awards and was awarded the National Medal of Arts by Ronald Reagan and the Presidential Medal of Freedom by George H. W. Bush.

Fitzgerald was born in Newport News, Virginia, the child of a common-law marriage between William and Temperance "Tempie" Fitzgerald. The pair separated soon after her birth and she and her mother went to Yonkers, New York, where they eventually moved in with Tempie's longtime boyfriend, Joseph Da Silva. Fitzgerald's half-sister, Frances Da Silva, was born in 1923. She and her family were Methodists and were active in the Bethany African Methodist Episcopal Church and she regularly attended worship services, Bible study, and Sunday School.

Sir Reginald Carey "Rex" Harrison (5 March 1908 – 2 June 1990) was an English actor of stage and screen. One of Harrison's best remembered film roles was that of Professor Henry Higgins in the stage and film versions of My Fair Lady. The role earned him a Tony Award, a Golden Globe Award and Best Actor Oscar.

Harrison was born in Huyton, Lancashire, and educated at Liverpool College. After a bout of childhood measles, Harrison lost most of the sight in his left eye, which on one occasion caused some on-stage difficulty. He first appeared on the stage in 1924 in Liverpool. Harrison's acting career was interrupted during World War II while serving in the Royal Air Force, reaching the rank of Flight Lieutenant. He acted in various stage productions until 11 May 1990. He acted in the West End of London when he was young, appearing in the Terence Rattigan play French Without Tears, which proved to be his breakthrough role.

Louis Armstrong (August 4, 1901 – July 6, 1971), nicknamed Satchmo or Pops, was an American jazz trumpeter and singer from New Orleans, Louisiana.

Coming to prominence in the 1920s as an "inventive" cornet and trumpet player, Armstrong was a foundational influence in jazz, shifting the music's focus from collective improvisation to solo performance. With his instantly recognizable deep and distinctive gravelly voice, Armstrong was also an influential singer, demonstrating great dexterity as an improviser, bending the lyrics and melody of a song for expressive purposes. He was also greatly skilled at scat singing (vocalizing using sounds and syllables instead of actual lyrics).

Renowned for his charismatic stage presence and voice almost as much as for his trumpet-playing, Armstrong's influence extends well beyond jazz music, and by the end of his career in the 1960s, he was widely regarded as a profound influence on popular music in general. Armstrong was one of the first truly popular African-American entertainers to "cross over," whose skin-color was secondary to his music in an America that was severely racially divided. It allowed him socially acceptable access to the upper echelons of American society that were highly restricted for a black man. While he rarely publicly politicized his race, often to the dismay of fellow African-Americans, he was privately a strong supporter of the Civil Rights movement in America.^{[citation needed]}

Cabell "Cab" Calloway III (December 25, 1907 – November 18, 1994) was an American jazz singer and bandleader. He was strongly associated with the Cotton Club in Harlem, New York City where he was a regular performer.

Calloway was a master of energetic scat singing and led one of the United States' most popular African American big bands from the start of the 1930s through the late 1940s. Calloway's band featured performers including trumpeters Dizzy Gillespie and Adolphus "Doc" Cheatham, saxophonists Ben Webster and Leon "Chu" Berry, New Orleans guitar ace Danny Barker, and bassist Milt Hinton. Calloway continued to perform until his death in 1994 at the age of 86.

Cab Calloway was born in a middle-class family in Rochester, New York, on Christmas Day in 1907. He lived there until moving to Baltimore, Maryland in 1918. His father, Cabell Calloway II, was a lawyer and his mother, Martha Eulalia Reed, was a teacher and church organist. When Cab was young, he enjoyed singing in church. His parents recognized their son's musical talent and he began private voice lessons in 1922. He continued to study music and voice throughout his formal schooling. Despite his parents' and vocal teachers' disapproval of jazz, Calloway began frequenting and eventually performing in many of Baltimore's jazz clubs, where he was mentored by drummer Chick Webb and pianist Johnny Jones.