I just added the upper image and entry to the 17th Century Timeline (1st half). It is noteworthy for a couple of reasons. 1) Although there are numerous frescoes that feature the trombone (for starters, browse the Trombone History Timeline), very few of them include this many depictions of the instrument. 2) Kloster Nonnberg (or Nonnberg Convent), the convent that houses this painting, is actually the Salzburg convent featured in the motion picture, “The Sound of Music.” Coincidentally, there is an additional trombone tie-in with “The Sound of Music”: the lower image below, a panel painting in the Mondsee, Austria parish church where, centuries later, the wedding scene in “The Sound of Music” is filmed, also depicts an angel playing trombone (c. 1682). In fact, the depiction of the angel-trombonist in the Mondsee church bears a resemblance to the two outer trombonists in the convent.

Nonnberg Convent fresco:

1625—Salzburg, Austria: A fresco by Matthäus Ostendorfer located in the Nonnenchor of Kloster Nonnberg (or Nonnberg Convent) features three angel-trombonists (see below image; public domain).

Mondsee church painting:

c. 1682—Mondsee, Austria: A panel painting in the Mondsee, Austria parish church (where, centuries later, the wedding scene in the motion picture “The Sound of Music” is filmed) depicts an angel playing trombone in the middle-bottom of the image (see below image) (Salmen, Bilder 57).