Which musical genre is characterized by a strong rhythmic groove and vocal improvisation that often addresses social issues?

The genre that best fits the description of being characterized by a strong rhythmic groove and vocal improvisation, particularly with a focus on social issues, is jazz. Jazz is known for its complex rhythms, syncopation, and the emphasis on improvisation, allowing musicians to express their creativity and respond in real-time during performances. This improvisational style extends not only to instrumental solos but also to vocal performances, where artists often incorporate spontaneous variations and riffs.

Moreover, jazz has a rich history of addressing social issues, particularly in relation to the African American experience, civil rights, and cultural commentary. Notable jazz musicians have often infused their works with messages that reflect societal challenges, giving the genre a profound relevance beyond just music.

In contrast, while the blues also features a strong emotional connection and often addresses themes of hardship and society, it does not emphasize improvisation to the same extent as jazz. Folk music tends to focus on storytelling and cultural narratives but usually lacks the rhythmic complexity associated with jazz. Rock music often has a strong groove but is less centered on vocal improvisation and social issues in the same way that jazz has been. Therefore, the distinct characteristics of jazz align perfectly with the query presented.