How does straight-ahead hard bop differ from the bebop of the 1940s and early 50s?

Straight-ahead hard bop, which emerged in the mid-1950s, differs from bebop primarily in its emphasis on a stronger rhythmic drive and a more pronounced blues and gospel influence. While bebop focused on intricate melodies and complex harmonies, hard bop incorporates more accessible, soulful themes and often features a more robust, swinging rhythmic feel. Additionally, hard bop musicians frequently utilized a fuller ensemble sound with a greater emphasis on the role of the piano and drums, moving away from the smaller, more intimate bebop combos.