Which musical techniques do ricercares share with later fugues?

The ricercare and the later fugue share a foundation in the extensive use of melodic imitation, where one or more themes are developed throughout the composition.1

Specifically, Venetian composers such as Andrea Gabrieli developed the ricercare using techniques that became hallmarks of the fugue, including:

• Stretto: The practice of playing the theme against itself with closely spaced, overlapping entrances.12
• Augmentation: Presenting the theme in longer note values.12
• Diminution: Presenting the theme in shorter note values.12

These techniques allowed composers to treat a single subject extensively, a structural approach that serves as a logical ancestor to the fully developed fugue. By the 18th century, the connection between these forms remained strong enough that Johann Sebastian Bach utilized the term ricercar for complex contrapuntal pieces in his Musical Offering, honoring the older form's tradition of rigorous imitative development.132