Both the standard and the alpenhorn look a little odd for an EIR Roman unit. Musical instruments in the Roman army at that point should look like this: Troops shown are a tubicen, with a tuba, on the right and a cornicen, with a cornu, on the left. Which is not at all to say you can’t use the figures you have. Just be aware that “caligae counters” may look at them sideways
Thanks, Mike. I did a bit more research on line last night and this morning. (I am away from my books just now.) The “alpenhorn” instrument is a lituus which my references seem to regard as being mainly used in funerals, processions by civilians but also in the army (mainly?) by the cavalry arm. It is based on an old Etruscan instrument. Here is one found near Dusseldorf
So I have an answer to the “caligae counters”.