These were worn for business and other important daytime activity, whereas the shorter, looser sack coat was worn for a leisurely day.
The frock coat and sack coat were both based on styles of the day.
Dark blue flannel sack coat - This coat was not tailored to the individual but was known for its comfort.
Many Union musicians wore a frock coat with a piping pattern across the front, but historical pictures make it clear that it wasn't uncommon for fifers and drummers to wear an undecorated frock coat or a sack coat.
Re-enactors can easily wear a plain frock coat or sack coat to portray band members during the Civil War and still be authentic for any period of the war.
