The 1920s showed a shift from melodic to improvisation.

The 1920s showed a shift from melodic to harmonic improvisation.

Explanation: Hi, the answer is harmonic improvisation.

The beginning of the 1920s, show a general shift from melodic to harmonic improvisation.  

Between the years 1920 and 1930, great soloists began to emerge as leaders, or members of different jazz ensembles. Some of these players included Louis Armstrong, a trumpeter with an unwavering grasp of swing, and some of the best improvisational skills a jazz musician had ever had, with very high range and fine tone.  

the main reason the us senate rejected the treaty of versailles was because "european nations wanted to punish germany"

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