Banjos and fiddles were the early instruments by all accounts, following on the Civil War. Mandolins became popular much later. The early photos we have research for various recording projects show a variety of instruments, including one great shot of cowboys in Alberta with an autoharp (not a zither). Guitars, modern stuff, aside, was not an instrument common with cowboys. For a good discussion of the bajo in the Civil War and later cowboy life go to www.drhorsehair.com; Bob Flesher's site. He has losts of disucssion and you can order a copy of the "The Banjo of the Cowboys"

Bob made the banjos shown in the film "Andersonville".

Another point to be made is that msot early "cowboy" music was acapella.

I doubt there were many insturment in the chuckwagon. There were other more important things to be carried.

Richard Wright