Admin reply: Howdy Merritt,
It was nice meeting you on Saturday night. Your question, which I assume relates to the fact that we often switch instruments, is a good one. A person who knew a lot about music could probably answer it better than I, but I'll give it a whirl.
It's true that many of the "bluegrass" instruments have different numbers of strings, and almost all of them are tuned differently than one another. However, there are certain relationships that exist between them with regards to tuning. An example would be that the four sets of strings on the mandolin are tuned to the same notes as the top four strings on the guitar--only on the mandolin they are arranged backwards from the order that they appear on the guitar. The same is true of the bass and the fiddle except that the notes are a couple of octaves apart. Instruments like banjos have several sort of "standard" tunings that are used frequently, but many of the same notes keep appearing in prescribed "patterns" that make them similar in relationship to the other instruments. Still and all the instruments and their tunings are different enough that most acoustic musicians simply treat them differently and try to learn on them as separate rather than learning them as "related" in how they should be approached. I hope this helps. RT

Added: April 12, 2008