Open Cmaj7 tuning
The open C major 7th tuning is an alternative tuning for guitar.
To get the open Cmaj7 tuning on your guitar you tune it like this: CGEGBE. The strings that differ from the standard should be turned so the string tension is decreased and not the opposite. The exception is the fourth string which should be tuned up from D to E. This will increase the tension on that string, but on the same time the total tension will decrease.
Including an octave perspective, the tuning is written C2-G2-E3-G3-B3-E4, meaning that the lowest string is a C note on the second octave, the second lowest string is a G note on the second octave and so on. Standard tuning reference: E2-A2-D3-G3-B3-E4.
There are obviously plenty of possible chord shapes for C major chords, which some are presented above.
Dm chords are more problematic because the open 4th string is E and not D as in standard tuning. The presented Dm chords are correctly written Dm11/C. The fingerings X00231 would result in Dmadd9/G and XX0231 would result in Dm/E. Notice also that the Dsus2 chord can be written as Dsus2/G.
Em chords cannot be played with the 6th open as in standard tuning.
F and G chords are quite hard to find natural shapes for in open position. G7 could however be played as X01003.
There are only a few of all voicing possibilities with open ringing strings suitable from the Open Cmaj7 tuning. If you want to go more into depth of this particular guitar tuning, see the Essential Chords in Open Cmaj7 Tuning ebook.
Progressions in this specific tuning:
Cmaj7 (000000) - Fmaj7 (555555) - Gmaj7 (777777)
Cmaj7 (000000) - C6/D (220010) - Em7 (440030)
More progressions with fingerings presented by diagrams can be found in the mentioned ebook above.
C Major 9th tuning
Related to the CGEGBE tuning presented here are the less known Open C Major 9th tuning: CGDGBE. Only two strings differ from standard tuning, which are the 5th and 6th strings; therefore, many fingerings are similar to that you are used to.
Some chords in Open Cmaj9 Tuning: