I think I would call that a transcription. There are lots of pieces that are transcribed for use by different instruments. For example, a Sousa march intended for a wind ensemble transcribed to be played on piano; or a Beethoven symphony transcribed for guitar, etc.
A transcription and a paraphrase are two different things. A transcription would be playing the same music, on a different instrument. For example: Brahms' transcription of the Chaconne in d minor, for left hand piano.
A paraphrase would be more along the lines of Liszt's Don Juan Fantasy: there are themes from the opera, but they are put in a new texture, invented by Liszt, not transcribed from anything Mozart wrote. He is using a condensed version of the opera, to make a new composition.
Walter Ramsey