Question about Mozart´s Rondo in K.311. No musical bars??

Hello everyone! I´m currently analyzing Mozarts Rondo of his K.311 for my Form and Analysis class. Let me give you the scoop:

Being a Rondo, the form would be like a Rondo, Scherzo or Minuet, so it would be A B A C A B A, now at the end of the C, mozart placed a small section, tempo Andante, which consists of just a single voice melody with no musical bar division... Now my question is... What is this? Is this common, and is there a name for it? It´s just there... And then the A section starts again.

thank you all!

Here´s an image!!



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I would call the section between the first fermata and the tempo primo a small cadenza. It does not start on the tonic in 2nd inversion, but functions as one nonetheless. "A cadenza in a piano sonata?" you may ask. See his Sonata in Bb Major KV333, iii movement, begining at bar 171. He even calls it "Cadenza." That one is more substantial and begins typically on the tonic in 2nd inversion. Perhaps you could just call the one you're looking at as a "Cadenza-like" passage? Otherwise you may be able to call it a fioritura.

 

Thank you very much!! I also received the same response from a fellow professor of my college, so I know I can trust you, and thank you for the extra bit of information, it´s a big help!