Actually, Astor Piazzolla didn't decide that traditional tango "had to" become art music. Rather, he longed to play and compose classical art music, and went to Paris to study classical/conservatory type composition with that goal. However, his efforts were unoriginal and lacking in his eyes, and he was frustrated. He was studying with Nadia Boulanger, an eminent classical pedagogue. When he expressed his frustration or disappointment regarding his compositional efforts, she asked him to tell her about his musical background. After he recounted his history of learning tango bandoneon from childhood and playing this Argentine traditional form, she exclaimed something like, "But this is your path!" to finding a voice as a composer of classical-type art music. ("Art music" being distinct from traditional dance music.) She urged him to draw on this as a foundation for his composition . . . And the rest is history. This music is ravishing and deeply moving. But . . it's art music, not dance music. You can do ballet to it, and you can do modern interpretive dance to it . . . but you can't dance the tango too terribly well to it. It does not have the beat and syncopation needed for tango dancing.
Which why traditional tango remains alive and well. And it sounds wonderful on the accordion!
