Many Tin-Pan Alley songs using thirty-two bar form are central to the traditional jazz repertoire. In jazz arrangements the word "chorus" refers to the same unit of music as in the Tin Pan Alley tradition, but unlike the Tin Pan Alley tradition a single song can have more than one chorus. Von Appen and Frei-Hauenschild explain, "The term, 'chorus' can also refer to a single iteration of the entire 32 bars of the AABA form, especially among jazz musicians, who improvise over multiple repetitions of such choruses."[4]