written by Broadway composers in the 1920s have become standards, such as George and Ira Gershwin's "The Man I Love" (1924), Irving Berlin's "Blue Skies" (1927) and Cole Porter's "What Is This Thing Called Love?" (1929). However, it was not until the 1930s that musicians became comfortable with the harmonic and melodic sophistication of Broadway tunes and started including them regularly in their repertoire. 1930s Broadway theatre contributed some of the most popular standards of the 1930s, including George and Ira Gershwin's "Summertime" (1935), Richard Rodgers and Lorenz Hart's "My Funny Valentine" (1937) and Jerome Kern and Oscar Hammerstein II's "All the Things You Are" (1939). These songs still rank among the most recorded standards of all time. The most popular 1930s standard, Johnny Green's "Body and Soul", was introduced in Broadway and became a huge hit after Coleman Hawkins's 1939 recording. 1930s saw the rise of swing jazz as a dominant form in American music. Duke Ellington and his band members composed numerous swing era hits that have later become standards: "It Don't Mean a Thing (If It Ain't Got That Swing)" (1932), "Sophisticated Lady" (1933) and "Caravan" (1936), among others. Other influential band leaders of this period were Benny Goodman and Count Basie. 1940s The swing era lasted until the mid-1940s, and produced popular tunes such as Duke Ellington's "Cotton Tail" (1940) and Billy Strayhorn's "Take the 'A' Train" (1941). With the big bands struggling to keep going during World War II, a shift was happening in jazz in favor of smaller groups. Some swing era musicians, such as Louis Jordan, later found popularity in a new kind of music, called "rhythm and blues", that would evolve into rock and roll in the 1950s. Bebop emerged in the early 1940s, with Charlie Parker, Dizzy Gillespie and Thelonious Monk leading the way. It appealed to a more specialized audiences than earlier forms of jazz, with sophisticated harmonies, fast tempos and often virtuoso musicianship. Bebop musicians often used 1930s standards, especially those from Broadway musicals, as part of their repertoire. Among standards written by bebop musicians are Gillespie's "Salt Peanuts" (1941) and "A Night in Tunisia" (1942), Parker's "Anthropology" (1946), "Yardbird Suite" (1946) and "Scrapple from the Apple" (1947), and Monk's "'Round Midnight" (1944), which is currently one of the most recorded jazz standard composed by a jazz musician. 1950s and later Modal jazz recordings, such as Miles Davis's Kind