It is hard for me to think of the solo as we know it today as being a relatively young invention in the history of music. Senior year of high school I was introduced to some of these first fledgling attempts at solos. The first recorded solo was from 1923 when King Oliver's Creole Jazz Band (which included Louis Armstrong) played "Dippermouth Blues." The song and the solo caught the country by storm, and became a an early "hit record." As Oliver's two-chorus solo draws to an end one member of the band shouts "Aww play that thing!" which became a popular shout of the mid-twenties. The first time I heard the song I labeled it as simple and boring, but what now excites me about this song and what excites me about all this music is both the intensity of these great musicians trying to invent a new skill while trying to invent a new form of music.
There are two other solos that I want to recommend. The first is George Mitchell's clarinet solo from Jelly Roll Morton's 1926 recording of "Doctor Jazz." He starts by holding one note for almost 12 bars as Morton plays his ragtime-inspired piano. Michell spends the next chorus building up energy through stop times and ends by holding the same note he began with for four bars setting up Morton's bombing voice singing "Hello Central, give me Doctor Jazz."
My favorite solo is by a young Louis Armstrong. Armstrong went through a number of changes early in his career. Beginning with his time under King Oliver's tutelage in New Orleans and Chicago and then moving to New York where he had been hired by Fletcher Henderson. In both these places Armstrong was concerned with energy, but also speed. And this won him the respect of older musicians and the admiration of younger musicians. He still was experimenting with the form of soloing when he made his famous Hot Five and Hot Seven recordings. But my favorite Armstrong period is when he begins to play fewer notes with more intensity. This is on full display on the 1936 recording of "Swing that Music." Armstrong sings for the first half, and it is hard not to fast forward this part. It is cliche, and boring; but then Armstrong picks up his trumpet and the entire sound changes. The band swings extra hard. And the energy is mind-blowing. During the entire last chorus Armstrong repeats one note -- and it's not boring.
Unfortunately, this style of soloing could not last in jazz as the art of improvisation was revolutionized first by Charlie Parker and Dizzy Gillespie, then by Art Blakey, Horace Silver, Miles Davis, John Coltrane, and lastly by Ornette Coleman and Eric Dolphy to name a few. And as the art of improvisation improved so did the theory behind the spur of the moment compositions and so did the complexity of the musicians comping the solos. Jelly Roll Morton's rag piano would be replaced by Al Haig's style of complex runs on chords that could climb up to including 8 notes (at least three of which were added on the performance and were different each time the section of the song came around). Against this background, Louis Armstrong's trumpet would be lost in the confusion. Some modern jazz musicians have tried to emulate the style of these early musicians, but not without feeling gimiky (there are a few exceptions, like Wynton Marsalis's album of Jelly Roll Morton songs, "Standard Time Vol. 6: Mr. Jelly Lord").
However, I recently discovered that for those looking for a more musically advanced solo that stays true to the simplicity and energy of the early jazz recordings there is hope in -- Rock music. My favorite of these musicians is Robbie Robertson, the guitarist for The Band. In many songs he limits himself to licks in the space between lines, but when he lets out a full solo it feels to come straight out of the tradition of Armstrong and Oliver. Check out Robertson's solos on "It Makes No Difference" or "Slippin' and Slidin'" or "King Harvest Has Surely Come." He is relatively slow, deliberate, simple -- and not boring.