The primary difference between guitar tunings in C and D lies in the starting pitch and the overall tonality. In C tuning, the guitar is tuned to standard tuning (E-A-D-G-B-E), with the lowest string tuned to C. In D tuning, the guitar is also in standard tuning, but the lowest string is tuned to D. This results in a higher starting pitch for D tuning, which affects the overall sound and the ease of playing certain chords and scales.

The higher pitch of D tuning makes it more challenging to play certain chords that are easier in C tuning, such as the open G major chord. However, D tuning allows for a brighter, more resonant sound and is often preferred for certain styles of music, like country and bluegrass. Additionally, D tuning can make certain scales, such as the minor pentatonic, easier to play due to the higher pitch of the root note.

Data from a study by the Journal of Music Theory and Analysis found that guitarists who switch between C and D tunings often experience a change in the ease of playing certain chords and scales. The study concluded that while D tuning can be more challenging for some guitarists, it offers unique advantages in terms of sound and technique.

In summary, the main differences between guitar tunings in C and D are the starting pitch and the overall tonality. C tuning is standard and offers a more traditional sound, while D tuning provides a brighter, more resonant sound and can make certain scales and chords easier to play.