Hello William et al,
To briefly answer your question, there are two aspects of music that are involved in each of the five Guards Regiments.
Each regiment have their own band, which is a complete orchestra, which Americans would compare to the Marine Corps Band. The Guardsmen who served with the band were given the rank of Musician.
In addition each regiment have a Corps of Drums (Except the Scots and Irish Guards who instead have a Corps of Pipes and Drums). The Corps of Drums consists of fifes, drums and bugles. From what I understand, each fifer carried a bugle, and depending on the situation would alternate between the two instruments as necessary. The Guardsmen who served with the Corps were given the rank of Drummer (whether they played fife, bugle or drum).
The Drummers certainly saw combat. If you look to the following article from our website, you will see that some such as Drummer Roe were called to give the ultimate sacrifice.
http://www.footguards.org/in_rem_roe.htm
I have always been of the understanding that the Drummers originally served as stretcher bearers on the front lines aiding and assisting the RAMC men in their work.
I hope this is helpful. From the reenacting standpoint, it is certainly an impression that can be done. With our morning parades, music is certainly called for, and they can then fall in as either a soldier or a stretcher bearer while in the trenches.
Regards,
Jim
Lt. J Higginbottom
BEF Company Officer (GWA)
2nd Grenadier Guards
Guards Division