Just added the following caption and picture to the 17th century timeline (first half). If you go to the post, Hi Ho Brass! Trombones on Horseback, you can see several other pictures of brave souls who apparently attempted the feat of playing the trombone while on horseback. Also, for more trombones in processions, see here and here.
1607—Dresden, Germany: A depiction of a portion of a procession features a trombone player and 3 shawm players on horseback (see below image; public domain) (Dresden, Sachsische Landesbibliothek).