I’m working on music for a band that has multiple parts and I will be playing the third part for my section, but I’m first for that part. There’s a section marked “soli”. Am I correct in assuming that it’s similar to a solo and do I play it? Like I’d think it’d go to first part but then why’s it in my music.
'Soli' generally refers to an exposed, soloistic part but played by several players or a whole section. Without seeing the score it's impossible to generalize, but it's possible that it's intended that only one player from each part plays. Your band director will explain what they want, but you should probably have the part prepared in case you have to play it.
'Solo' is a featured passage for one player. 'Soli' is a featured passage for more than one player or instrument.
It may mean the whole trombone section play it. Like 'Heads up, guys! You've got the tune!' Or that just one player on each part is to play. I think we can assume that if it's in the third part, at least SOMEONE from that section will play it!