Although early jazz music featured a great deal of improvisation, this improvisation did not stray too far from the rather simple, catchy melodies upon which it was based. So, however interesting it may be, later music featuring improvisation that strays far from the melody ought not to be classified as jazz. Which one of the following, if true, most weakens the argument? ['Some of the later music featuring improvisation was performed by artists who had been jazz musicians earlier in their careers.', 'For a piece of music to be classified as jazz, it must feature some amount of improvisation .', 'The later music featuring improvisation has much more in common with early jazz than with any other type of music.', 'Many types of music other than jazz feature a great deal of improvisation.']