Final answer:
Improvisations for silent films were based on prevailing musical styles such as jazz and blues, enhancing the movie experience by matching the screen action.
Step-by-step explanation:
Pianists' or organists' improvisations for silent films of the 1910s and 1920s were often based on the prevailing musical styles of the time, which included genres such as jazz and blues. These improvisations were used to enhance the movie experience by matching the mood and actions on screen and were an essential part of the silent film era. Jazz was particularly influential in this period, as it provided a bold rhythm and harmony that could vividly accompany the highs and lows depicted in silent films. Moreover, performers like Paganini and Liszt, regarded as the pop stars of their day, had already popularized the idea of musical improvisation before this period.