Hi Jon,
Your question intrigued me as I'm busily working on some Highland regiments myself. As I understand it, traditionally in the British army trumpets were used by the light infantry companies and drummers and fifes with the grenadiers and middle companies. However I have never seen a Highlander modelled or illustrated as a trumpeter. I did read somewhere that even in non-kilted Highland regiments the piper might still be permitted a kilt.
I searched around a bit on the web and this was all I found that might apply (not much help):
http://theminiaturespage.com/boards/msg.mv?id=426099Drummers were on the strength, entered in the rolls separately from enlisted men and sergeants. However, the Crown was not responsible for musicians. Highland regiments were allowed to enter two pipers as drummers in the grenadier coy. Any more had to be paid for by the officers of the regiment, or the Colonel if he was so disposed, which was not always the case.
https://www.halifaxcitadel.ca/music/the-pipes-and-drums-of-the-78th-highlanders.htmlFor centuries, pipers have led men of the Highland Clans into battle. In the 18th & early 19th centuries, pipers in Highland regiments, usually played alone, not until the Napoleonic period did they begin playing together on the march. During the mid-1800s pipers and drummers began playing together, prior to which drummers played with fifers. In times of war the pipes and drums played on the line of march and during battle, serving an important psychological purpose, the music a boost to the morale and fighting spirit of the men.