Most modern jazz is based around 70s style funk and is heavily influenced by classic rock which although when all separate are great things do not combine to make a viable music genre.
Many old school jazz musicians are household names, although it is becoming rarer and rarer to see a jazz CD or record in someones home. A few examples would be John Coltrane, Louis Armstrong, Miles Davis, Glenn Miller, Duke Ellington, and Ella Fitzgerald.
This music was first started with the ragtime movement in the late 19th century where piano tunes such as the Maple Leaf Rag and The Entertainer by Scott Joplin were played in bars and saloons all over the country.
Soon thereafter a mixture of soul, gospel and French music formed in New Orleans and formed the famous New Orleans brass band type of music. A good example of this is "The Saints Go Marching In" by Louis Armstrong
These generally happy Dixieland songs coexisted with the blues until the great depression era when Swing Music and Big Band took hold. Swing and Big Band Music such as Glenn Miller, Duke Ellington, Benny Goodman and Count Basie were easily danceable tunes played for large audiences during the horrors of the Great Depression to relieve the tension of the times. This type of music persisted until the post WW2 era when musicians began making the greatest type of music for themselves
In the beatnik era of the late 40s thru 40s Bebop jazz took hold which was an incredibly fast and tough to play style meant to challenge the best of the Jazz musicians. In this period Jazz musicians received artistic liberation because now they formed quartets and quintets making music the challenge their mind body and soul.
The Last chapter of old jazz was about in the late 50s when smooth jazz took hold as music for intellectuals. Miles Davis and John Coltrane successfully switched over from Bebop to smooth and cool jazz in this era.