There was a similar question the other day about the piano playing around the melody between the phrases of the vocal soloist:
I'd name this "paraphrasing".
look up wiki paraphrase wiki English
or paraphrase musik wiki de
I didn't find a link in English paraphrase music
and I don't know whether there exists another term than soloing.
Paraphrasing Defined
We've all watched television shows or heard news stories we wanted to tell others about. We may have told our friends, our family, or our coworkers about what happened, how it happened, and why it happened. We recounted the storyline, the main characters, the events, and important points using our own words. This is paraphrasing - using your own words to express someone else's message or ideas. In a paraphrase, the ideas and meaning of the original source must be maintained; the main ideas need to come through, but the wording has to be your own.