How did tango music and dance style change after the early 1900s?

Following its rise to social prominence in the early 1900s, the tango underwent significant transformations in both music and movement:

Musical Evolution

• Mood and Tempo: Early tangos were spirited and lively, but by 1920, the music shifted toward an intensely melancholy tone, often featuring lyrics filled with nostalgia and bitterness.12
• Structural Changes: The prevailing duple meter (${}^2{/}_4$) evolved into ${}^4{/}_4$, ${}^4{/}_8$, or other tempos.1
• Innovation: In 1955, musician Astor Piazzolla began creating tango nuevo, which blended traditional elements with jazz and classical music, incorporating new rhythms, harmonies, and counterpoint.3

Dance Style Evolution

• Technique: The dance evolved from early, exuberant movements into a smoother ballroom step. As it gained popularity in Europe, it adopted a lifted body carriage and specific movements like dips, mechanical stops, and quick weight shifts.12
• Complexity: During the 1930s and 1940s, the dance expanded to include more complex steps such as ganchos (leg hooks), saltos (jumps), and boleos (flicks).2
• Embrace: The original close embrace relaxed to accommodate these new, more intricate leg gestures and variations.2