This was a format used (and popularized) by both Parker (alto sax) and Gillespie (trumpet) in their 1940s groups and recordings, sometimes augmented by an extra saxophonist or guitar (electric or acoustic), occasionally adding other horns (often a trombone) or other strings (usually violin) or dropping an instrument and leaving only a quartet.

Bebop differed drastically from the straightforward compositions of the swing era and was instead characterized by fast tempos, asymmetrical phrasing, intricate melodies, and rhythm sections that expanded on their role as tempo-keepers.

The music itself seemed jarringly different to the ears of the public, who were used to the bouncy, organized, danceable compositions of Benny Goodman and Glenn Miller during the swing era.

Typically, a theme (a "head," often the main melody of a pop or jazz standard of the swing era) would be presented together at the beginning and the end of each piece, with improvisational solos based on the chords of the compositions.

This unprecedented harmonic development which took place in bebop is often traced back to a transcendent moment experienced by Charlie Parker while performing "Cherokee" at Clark Monroe's Uptown House, New York, in early 1942.

I was working over "Cherokee", and, as I did, I found that by using the higher intervals of a chord as a melody line and backing them with appropriately related changes, I could play the thing I'd been hearing.

It came alive.Gerhard Kubik postulates that the harmonic development in bebop sprang from the blues, and other African-related tonal sensibilities, rather than twentieth century Western art music, as some have suggested.

Kubik states: "Auditory inclinations were the African legacy in [Parker's] life, reconfirmed by the experience of the blues tonal system, a sound world at odds with the Western diatonic chord categories.

Bebop musicians eliminated Western-style functional harmony in their music while retaining the strong central tonality of the blues as a basis for drawing upon various African matrices.

[12] Bebop grew out of the culmination of trends that had been occurring within swing music since the mid-1930s: less explicit timekeeping by the drummer, with the primary rhythmic pulse moving from the bass drum to the ride cymbal; a changing role for the piano away from rhythmic density towards accents and fills; less ornate horn section arrangements, trending towards riffs and more support for the underlying rhythm; more emphasis on freedom for soloists; and increasing harmonic sophistication in arrangements used by some bands.

He was especially enthralled by their tenor saxophone player Lester Young, who played long flowing melodic lines that wove in and out of the chordal structure of the composition but somehow always made musical sense.

[citation needed] The brilliant technique and harmonic sophistication of pianist Art Tatum inspired young musicians including Charlie Parker and Bud Powell.

[15] One of the divergent trends of the swing era was a resurgence of small ensembles playing "head" arrangements, following the approach used with Basie's big band.

[17] Part of the atmosphere created at jams like the ones found at Minton's Playhouse was an air of exclusivity: the "regular" musicians would often reharmonize the standards, add complex rhythmic and phrasing devices into their melodies, or "heads", and play them at breakneck tempos in order to exclude those whom they considered outsiders or simply weaker players.

Christian and the other early boppers would also begin stating a harmony in their improvised line before it appeared in the song form being outlined by the rhythm section.

The sessions also attracted top musicians in the swing idiom such as Coleman Hawkins, Lester Young, Ben Webster, Roy Eldridge, and Don Byas.

Some sessions at Minton's in 1941 were recorded, with Thelonious Monk alongside an assortment of musicians including Joe Guy, Hot Lips Page, Roy Eldridge, Don Byas, and Charlie Christian.

Hawkins led another bebop-influenced recording session on October 19, 1944, this time with Thelonious Monk on piano, Edward Robinson on bass, and Denzil Best on drums (On the Bean, Recollections, Flyin' Hawk, Driftin' on a Reed; reissue, Prestige PRCD-24124-2).

On January 4, 1945, Clyde Hart led a session including Parker, Gillespie, and Don Byas recorded for the Continental label (What's the Matter Now, I Want Every Bit of It, That's the Blues, G.I.

Gillespie recorded his first session as a leader on January 9, 1945, for the Manor label, with Don Byas on tenor, Trummy Young on trombone, Clyde Hart on Piano, Oscar Pettiford on bass, and Irv Kluger on drums.

Parker appeared in Gillespie-led sessions dated February 28 (Groovin' High, All the Things You Are, Dizzy Atmosphere) and May 11, 1945 (Salt Peanuts, Shaw 'Nuff, Lover Man, Hothouse) for the Guild label.

Sir Charles Thompson's all-star session of September 4, 1945 for the Apollo label (Takin' Off, If I Had You, Twentieth Century Blues, The Street Beat) featured Parker and Gordon.

Bebop was taking root in Los Angeles as well, among such modernists as trumpeters Howard McGhee and Art Farmer, alto players Sonny Criss and Frank Morgan, tenor players Teddy Edwards and Lucky Thompson, trombonist Melba Liston, pianists Dodo Marmarosa, Jimmy Bunn and Hampton Hawes, guitarist Barney Kessel, bassists Charles Mingus and Red Callender, and drummers Roy Porter and Connie Kay.

Gillespie's "Rebop Six" (with Parker on alto, Lucky Thompson on tenor, Al Haig on piano, Milt Jackson on vibes, Ray Brown on bass, and Stan Levey on drums) started an engagement in Los Angeles in December 1945.

Gillespie, with his extroverted personality and humor, glasses, lip beard and beret, would become the most visible symbol of the new music and new jazz culture in popular consciousness.

Around that same time, a move towards structural simplification of bebop occurred among musicians such as Horace Silver and Art Blakey, leading to the movement known as hard bop.

Voicing experiments based on bebop harmonic devices were used by Miles Davis and Gil Evans for the groundbreaking "Birth of the Cool" sessions in 1949 and 1950.

[18][19] The "beatnik" stereotype borrowed heavily from the dress and mannerisms of bebop musicians and followers, in particular the beret and lip beard of Dizzy Gillespie and the patter and bongo drumming of guitarist Slim Gaillard.

Bassist Ron Carter collaborated with A Tribe Called Quest on 1991's The Low End Theory, and vibraphonist Roy Ayers and trumpeter Donald Byrd were featured on Guru's Jazzmatazz, Vol.

Bebop samples, especially bass lines, ride cymbal swing clips, and horn and piano riffs are found throughout the hip-hop compendium.