Task: Question Answering
Input (English): Passage: In New Orleans, jazz had traditionally been expressed through polyphonic ensemble playing, with the various instruments weaving their parts into a single and coherent aural tapestry. By the early 1920s, developments in jazz saw the rise of the jazz soloist, with solos becoming longer and more complex. Both Beiderbecke and Armstrong were key figures in this evolution, as can be heard on their earliest recordings. According to the critic Terry Teachout, they are "the two most influential figures in the early history of jazz" and "the twin lines of descent from which most of today's jazz can be traced."Beiderbecke's cornet style is often described by contrasting it with Armstrong's markedly different approach. Armstrong was a virtuoso on his instrument, and his solos often took advantage of that fact. Beiderbecke was largely, although not completely, self-taught, and the constraints imposed by that fact were evident in his music. While Armstrong often soared into the upper register, Beiderbecke stayed in the middle range, more interested in exploring the melody and harmonies than in dazzling the audience. Armstrong often emphasized the performance aspect of his playing, while Beiderbecke tended to stare at his feet while playing, uninterested in personally engaging his listeners. Armstrong was deeply influenced by the blues, while Beiderbecke was influenced as much by modernist composers such as Debussy and Ravel as by his fellow jazzmen.Beiderbecke's most famous solo was on "Singin' the Blues", recorded February 4, 1927. It has been hailed as an important example of the "jazz ballad style"—"a slow or medium-tempo piece played gently and sweetly, but not cloyingly, with no loss of muscle." The tune's laid-back emotions hinted at what would become, in the 1950s, the cool jazz style, personified by Chet Baker and Bill Evans. More than that, though, "Singin' the Blues" has been noted for the way its improvisations feel less improvised than composed, with each phrase building on the last in a logical fashion. Benny Green describes the solo's effect on practiced ears:
When a musician hears Bix's solo on 'Singing the Blues', he becomes aware after two bars that the soloist knows exactly what he is doing and that he has an exquisite sense of discord and resolution. He knows also that this player is endowed with the rarest jazz gift of all, a sense of form which lends to an improvised performance a coherence which no amount of teaching can produce. The listening musician, whatever his generation or his style, recognizes Bix as a modern, modernism being not a style but an attitude. 
Question: What is the name of the solo work that is an important example of the "jazz ballad style"?
Output (English): Singin' the Blues.