Dixieland is one of the true old-style Jazz varieties, which developed mainly
in Chicago in the mid-20s. The music style is very characteristic - a sort of
mixture between Classic Jazz and New Orleans jazz. The style has also been
dubbed Chicago jazz.
The style is famous for beginning with collective improvisation,
with the song usually "evolving" into famous tunes - often ragtime,
Swing or classic jazz licks.
Dixieland had a revival in the 50s - it became a major fad
that quickly faded away, because the musical prestations were eclipsed by sillyness
(Straw hats, silly dances, colorful suspenders and other disturbances)
Instruments that were frequently in use included brass instruments,
saxophones and banjos(!)
Dixieland has a much more playful feel to it than traditional
jazz has. The tunes are more joyful and the rhythmic banjos n the background
(playing much of the same role as rhythm guitars have in modern rock music)
enforce this feel even more. The improvisations are usually short, deliberate
and stacatto tones rather than the fast, flowing "shape" that regular
Jazz tends to have.
A "standard" Dixieland tune (if there is such a thing)
has a lead instrument that gets the band going. Usually, the lead instrument
plays around for a bit, with the drums and bass (and other intstruments) following
quickly afterwards. More often than not, the tune takes shape of a famous
tune (as mentioned). Solos are usually short (2-4 bars) and follow each other
in quick sucession. A solo usually imitates a part of the previous solo, and
adds something new (you get a relay race feeling, really).
(thank you, DejaMorgana for suggesting improvements to this node)