Wow, that’s some wonderful stuff! I may need to pick up one of those recordings, (or both).
But I’d hardly classify it as American “old-time”. The clips I sampled were very Celtic-rooted, and not the southern mountain music that I think Diane was originally asking about. I really can’t think of any recorded “old-time” stringbands that employ much in the way of wind instruments.
My band (shameless plug) does OT music from the 19th century and beyond, and we have always had a pennywhistler. Our “Campfire” CD (http://www.heritagestringband.com/music.htm) features pennywhistle on nearly every cut. The musically inclined of the period played whatever instruments they happened to have or could make. Some instruments, such as the fife and drum, were familiar to the soldiers of the Civil War and were played in what we now call “jams.” I don’t know of any specific inclusions of the flute, but why not? My band will have a flute as soon as I am satisfied with my playing.
Some OT players express annoyance at the arrival at a session of any instrument not considered OT, and there is little you can do about that except keep a low profile until everyone feels comfortable with your flute playing.