guitars

Learn a lot of Bluegrass songs and you'll get a feel for what chords go together - Bluegrass does not tend to use a lot of Jazz chords, but you will need a capo.

Look at the white keys on a piano, starting at C (white key next to the two black keys rather than three). The intervals between those white keys are TTSTTTS (tones and semitones). If you play C-E-G, you get a Cmajor chord. Now, if you take those three fingers and work your way up the keys, always skipping one key, the chords you will get are C, Dm, Em, F, G, Am, Bdim, and back to C.

If you start at any note on the keyboard, and figure out the TTSTTTS pattern from there (G is an easy one, the notes of the G Diatonic Scale are G-A-B-C-D-E-F# and back to G - the farther away you get from C in the circle of fifths, the more Flats or Sharps (Accidentals) will be in the scale),

Anyways, you can follow that same pattern and you'll that same sequence of Maj-Min-Min-Maj-Maj-Min-Dim, which are called Diatonic Chords. Basically, all these chords fit together beautifully with each other, in various combinations, with the most common set being the I-IV-V, which in C corresponds to C, F and G - the roman numerals refer to the chord you find at a given step in the diatonic chord scale. So for the G scale, your chords would be G-Am-Bm-C-D-Em-F#dim.

But there are all kinds of ways to mess with that basic harmonious formula, that I will not get into here, but find yourself a good theory course and go all the way through it. But mostly, learn those Bluegrass classics, and realize just how many are mostly I-IV-Vs with some tricky little bits thrown in here and there - it's not Jazz and never tries to be, though there is virtuosity everywhere.