Consider the Intrada con Trezza in D minor by J.H. Schmelzer. The score has two movements: Intrada followed by Treza.
I wondered whether a Trez(z)a is some kind of musical form (like Menuet etc.).
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Treza is often referred to as "trio" — the middle section of a ternary form piece. In this case it is also in triple meter.
One listing for the term can be found in A New Musical Grammar and Dictionary or, A general Introduction to the Whole Art of Musick by William Tans'ur (1756, ISMLP)
Tertia, Treza, Trezzeto — Three parts
There is a recording of "Partita in C major: Adagio. Aria. Treza. Ciacona" by Michael Praetorius.
About more about trios and their origins on this site:
Note: It is possible that the term emerged as a mis-spelling of "terza" (third), perhaps having been confused with "tre" (three).
The word "terza" meaning "third" appears in Queen Anna's New World of Words, or Dictionarie of the Italian and English Tongues (1611) by John (Giovanni) Florio, page 559.
Terza, the third in order.
The possibility of error in the use of the word is reinforced by Corelli, who was himself Italian, composed in the late 1600s, and used the word "terza" (meaning "third in order", as opposed to referring to the trio portion of a piece).
Here is the beginning of the third of his "Twelve Trio Sonatas" Op. 1, "Sonata Terza".
(Image source: IMSLP, First edition)