TromboneChat

I have a grip and experience of performing simple improvisation and am comfortable with it. Have been asked to join in with a group of assorted musicians playing at the funeral of a respected mutual friend. No idea who will turn up on the day.
We’ve been given the names of the songs and keys and it looks straightforward. It’s New Orleans style brass band - Dejuan’s Olympia Brass Band is the suggested reference point.
No problem playing the melody but looking for tips and advice on how to best accompany, back up and fill when the melody/solo is elsewhere.
My working assumption is that less is more, play in the spaces, provide runs into chord changes etc. Any advice about fitting in musically to this sort of informal group set up?

The New Orleans Brass Band is a descendent of the "Sousa Band" of the late 19th century. As such, a set of roles became associated with different instruments: Cornet plays melody; Clarinet plays obbligato above the melody; trombone takes the Euphonium role of playing a counter-melody. Other members of the band have the same functions they would have had in the Sousa Band, although the chordal instruments (banjo, piano, guitar) simply support the rest of the ensemble.

As the trombone, don’t ever underestimate the value of underlining or filling out the basic motor rhythms like bamboula or habanera during tutti sections.

Another way of thinking about potential trombone parts in this style: as a trombone kind of equivalent to a rhythm guitar part in a funk band.

Thanks everyone. The funeral took place last week. A veritable forest of trombones, he was a trombonist, and other instruments too. Playing and non-playing musical mourners were positive about the music. Your tips were useful and I tried to bear them in mind.