David Hamburger talks about the open-C tuning as a favorable alternative to the more familiar open-D and open-G tunings in this excerpt from Alternate Tunings Guitar Essentials.
As guitar players we sometimes think of blues and country as being two completely different worlds, one thumpy and droney and shuffle-based, the other bright and sprightly and uniformly two-beat. Of course, blues and country have been cross-pollinating for a good long time, whether the results are the relaxed lilt of Mississippi John Hurt doing an old murder ballad or Merle Travis squeezing out jazzy chord licks over a poppin’ two-beat feel. In this lesson we’ll take a look at open-C tuning and start developing a countrified blues vocabulary that will work over an alternating-thumb bass. Open C’s lower bass register and higher intervals on top make for some interesting voicing and single-note possibilities that are worth exploring, and it’s a flavorful alternative to the more familiar open-D and open-G tunings.
If you’re at all familiar with open-D or open-G, you’ve got some reference points already for checking out open-C. The basic idea is the same: strum all the open strings and you get a big fat chord; form your IV and V chords by either barring at the fifth and seventh frets or make alternative voicings in the open position that may or may not have the root of the chord as the bottom note.
To get into open-C tuning, tune the low E string down two whole steps to C. Bring the A string down a whole step to G and the D string down a whole step to C. Leave the G string where it is, raise the B string a half step to C, and leave the high E string alone. From low to high, the tuning is: C G C G C E.
We’ll stick with three basic open-position voicings for this lesson, since our emphasis is going to be on working out various licks and melodies over the I, IV, and V chords. Here are the voicings we’ll be using for C, F, and G:
As you may know if you’ve done any single-note blues soloing with another guitar player or a band, one of the great beauties of the minor pentatonic scale is the way the same phrases seem to work over all three chords of a blues progression. Here’s one fingering for an octave and a half of the C-minor pentatonic scale in open position:
Now let’s try playing a simple phrase worked out over an alternating-thumb accompaniment with a C chord, an F chord, and a G chord:
Excerpted from Alternate Tunings Guitar Essentials.