A word for an instrumental melody which copies the vocal part?

Sometimes in rock music you'll hear a guitar solo which reproduces the vocal melody: from the verse, for example.

Smells Like Teen Spirit by Nirvana springs to mind - here's a link to the relevant part, just before the solo starts. https://youtu.be/hTWKbfoikeg?t=161

Can anyone think of a neat, ie terse but with a clear meaning, way to describe such an instrumental solo?

Something with a meaning similar to "vocal-melody-copying", but nicer. If there's already an Italian word for this from the world of classical music, then that's fine.

I usually associate “an instrumental reprise” with an instrumental version of an entire song that was originally written with vocals, like the instrumental version of the Eagles' Wasted Time discussed in paragraph three of the “Song Facts” link.

However, this link seems to be using “instrumental reprise” (and the less ambiguous “instrumental response”) to describe what you are seeking:

The first verse is sung to the accompaniment of the instrumentalists; this is followed by an instrumental reprise of the melody in slightly altered form known as the jawab “response.” The second [sung] verse is then … [also] followed by the slightly different instrumental response.

(from The Concise Garland Encyclopedia of World Music, Volume 2 edited by Ellen Koskof, via ‘Google Books’)

Of these two, “instrumental response” would be less likely to cause confusion with the “instrumental version” meaning of "instrumental reprise," but "response" would imply that the instrumental solo is somehow different from the vocalized melody, whereas "reprise" would capture better the notion of it being "copied" or "repeated" instrumentally.
("In music, a reprise ... is the repetition or reiteration of the opening material later in a composition ..." from Wikipedia.)

His solo was an instrumental reprise of the song's/the verse's [vocalized] melody.

While it's not a single word, sometimes this is referred to as "restating the melody." The section itself would still be called a solo, if one player is featured, or an instrumental break, if it's an ensemble.

...the sax player who steps forward to restate the melody in the middle of a song is also soloing.

Complete Idiot's Guide to Solos and Improvisation (Google Books)

The word you are looking for is a musical lead. Typically it is because that part will play at the same time as the vocals "lead"ing them. However, it qualifies regardless of the order they are in the song.

Incidentally, this is also why the main guitar is called the lead guitar. Not because it's the main one and thus the leader, but because it plays the lead part.

The closest musical term I can think of is eco: an effect in which a group of notes is repeated, usually more softly, and perhaps at a different octave, to create an echo effect.

What you describe also has some similarities with a call and response, but in that case the two musical phrases are usually different.