Trombones have gone through more permutations than some people may realize. Not only has history seen soprano, alto, tenor, bass, contrabass, and valve trombones, but an intriguing permutation of the instrument, called the rear-facing or over-the-shoulder trombone, pops up frequently in pictures and occasionally in museum holdings; e.g., here. For a YouTube clip of someone playing such an instrument, see here. (I prefer rear-facing as a descriptive term, since over-the-shoulder does not distinguish from the standard trombone, which, unlike the other brass instruments, already has a rear bow of tubing that extends over the player’s shoulder.)
Today I added the below 2 images, with their captions, to the Trombone History Timeline (16th century) and to the collection, Backward Advances: Rear-Facing Trombones Throughout History, which now contains well over 60 examples of the instrument, at least 9 of which are from pre-19th century.
c. 1504—Perpignan, France: A painting on an organ shutter (since relocated to the wall opposite the organ) in the Perpignan Cathedral (Cathedral Basilica of Saint John the Baptist of Perpignan, or Basilique-Cathédrale de Saint-Jean-Baptiste de Perpignan) depicts musicians at the Feast of Herod, including a rear-facing or over-the-shoulder trombone. Although there are some improbable aspects of the trombone, including the shape of the slide and the general configuration of the tubing, it seems unlikely that the artist would have misjudged the actual direction of the bell (see below detail; public domain; special thanks to Jean-Jacques Herbin). The rear-facing or over-the-shoulder trombone is one of several examples from pre-1800, including 1503-1529, c. 1504, 1570, 1578, c. 1615, c. 1660-1670, 1689, 1732, and c. 1795.
1570—Waiting for the Princely Guests, an image depicting wind musicians in a balcony atop a triumphal arch, shows trombone, trumpets, bombard, and positive organ, as they prepare to play for a prince’s arrival (see below image; public domain) (Carter, Renaissance 278; Nuremberg, Stadtbibliothek). The rear-facing or over-the-shoulder trombone is one of several examples from pre-1800, including 1503-1529, c. 1504, 1570, 1578, c. 1615, c. 1660-1670, 1689, 1732, and c. 1795.