I suggest learning to play "Boil Dem Cabbage" in the keys of D, G and A. Best if you memorize them, but it's not required.

Not only does "cabbage" cover the three major chords in that key, it's also the order in which they're most likely to appear.

Here's what I mean: If you think of Cabbage not as a song, but as a "chord progression" or more simply, the order in which the songs appear, you start to see those same patterns elsewhere. For example....

Cabbage chord progression: D - G - D - A - D - G - D - A - D
Amazing Grace progression: D - G - D - A - D - G - D - A - D

Look familiar?

Note, that I am not referring to the time signature (one is a waltz, one is not) nor am I referring to how long you hold each chord (those are different too). BUT if you playing one chord you have a pretty good guess at what the next one will be.

Also, there are only 3 chords at play, so you have a 50/50 shot at getting right anyway. :-)

Here's an experiment, play Cabbage while a friend plays the B section of "Soldier's Joy". You'll see they work pretty well. The A section works too, if you skip the G chords and just stick to the A.

Even if the song's chord progression is different from Cabbage it's not completely different, more like "intentionally different"

  Cabbage:  D - G - D - A - D - G - D - A - D

Southwind: D - A - D - G - D - A - D - G - D

Note that Southwind STILL returns to the D after each new chord, just like Cabbage. Really, in many ways, its just Cabbage played backwards. And oh yeah, The B section of Southwind? It's just Cabbage in 3/4

Of course there are always exceptions, and this doesn't apply very well to minor key songs like "Shady Grove" or "Cold, Frosty Morning." But if you want to stay involved with tunes you don't know (which I HIGHLY recommend). This can help a lot.

The 1 1/2 fret does not effect your ability to play chords, just ignore it when figuring out where to place the fretting fingers of your left hand.  The 1 1/2 fret may increase the number of chords available to you, but it won't change the fretting positions of those chords already known.

Just be sure to think of that fret as the 1 1/2 fret, and don't be tempted to rename it the 2nd fret.  You already have a 1st and a 2nd fret, so the one in between fret 1 and fret 2 is logically called the 1 1/2 fret.  

If you take Dusty's great suggestion to use a chord chart, the fret numbers (including the 1 1/2 fret when needed) are clearly indicated on the chord charts.

If you decide to use a capo, it will raise the key and change the name of the chord shapes accordingly, but the actual chord shape formed by your left hand remains the same.

Don, you've gotten some good advice here.  As Robin has pointed out, the main keys for folk music are C, D, G, and A, and Skip has explained how to figure out the important I, IV, and V chords in those keys.  You can use any chord chart, such as those Stephen Seifert makes available , to learn how to play those chords.  You should also be aware of how versatile the barre chord is.  I assume you can count to 7 and you know the alphabet. If 000 is a D chord, then 111 is an E chord, 222 is an F (really F#) chord, 333 is a G chord, 444 is an A chord, 555 is a B chord, and 666 is a C chord.  Then we start over with D again at 777. Until you learn more chord voicings, those are safe places for you.

Personally, I prefer to approach this by using a capo, which enables me to play in D, G, and A out of a DAd tuning, and then tuning down a step to CGc to play in C.  Then I only have to learn the chord positions for one key but they will work in the others.  What I mean by that is that 002 is a D chord when tuned DAd, a G chord with the capo at 3, an A chord with the capo at 4, and a C chord when tuned CGc.  So I consider that a I chord rather than remembering four different chord names.  The same with the 013.  That's a G in DAd, but a C with the capo at 3, a D with the capo at 4, and an F when tuned CGc.  I could memorize all that or I could just think of it as a IV chord.  I could go on, but hopefully you see my point. 

I explain this approach in a document I've attached which was written for a different but related question, and also includes a transposition chart for the major keys.  And you can see me demonstrating how to use a capo to move to the keys of G and A this video here .

strumming in various keys out of DAd tuning.pdf  •  22KB

Don;

You can figure out the chords and the notes to each chord using one hand. Here's how; Looking at your left had, palm up, the thumb = the key note name/I chord name, the ring finger = the IV chord and the little finger = the V chord. To determine the notes to a chord, [you need to know the notes in the scale] ; thumb = base/chord name [root] , middle finger =  the 2nd or middle note [Major 3rd] ; the little finger = the 3rd or high note [Perfect 5th] . By the way, the other fingers represent the ii, iii, vi, and vii notes/chords. The real challenge is to find the notes on your MD.

Using a 158 tuning, like DAdd, the basic I [D] chord is 0 fret/open; IV [G] chord is 013/310; V [A] chord is 101. These are the same frets to play the I, IV, and V chords in any key using a 158 tuning. You would have to change the tuning to CGC use this for C or AEA for A, etc. You should go the route of previous posts for a more in depth study.

Don, something which served me well was attending several jams to observe & listen before I ever tried to play in a jam.  The skill of jamming-- playing called tunes 'on the fly'-- takes time for some of us to acquire.  I know it took me awhile.    

Don -- look on the Strothers Chord Finder __ http://strothers.com/chords.html  or one of the dozens of dulcimer chord finder charts available to download.

Don, my guitar-playing husband says for the Keys of A, C, D, and G, especially, it is good to know the I, IV, V chords. 

I'll bet those are the same chord progressions that guitar players use when playing accompaniment rather than melody.

Knowing those progressions would certainly save on the reams of paper that most people collect of jam tune tabs and carry around with them.  Save having to sight-read or memorize words and tunes as well.

Are there chord progressions I should know for jams?