The "Open Cmaj9/13" tuning offers a truly unique and expansive sonic landscape, immediately setting itself apart from conventional tunings. As its name suggests, when strummed open, this tuning beautifully articulates a rich, complex C Major 13th chord (C-E-B-D-A-E). This creates an immediate lush, jazzy, and resonant sound, perfect for introspective pieces, ambient textures, or songwriting that demands a sophisticated harmonic foundation.

Technical Analysis

The open notes are, from lowest to highest: C2 - E2 - B2 - D3 - A3 - E4. What makes this tuning particularly fascinating, as highlighted by its original description, is its "weird downtuning based around the interval of the perfect fifth." While the lowest two strings (C2 to E2) form a Major 3rd, the subsequent string pairs reveal striking perfect fifth relationships: E2 to B2, D3 to A3, and A3 to E4. This cluster of three consecutive perfect fifths (on strings 5, 4, 3, 2, 1) is highly unusual for standard guitar tuning and opens up unique melodic and harmonic possibilities.

Harmonically, the open tuning offers:

• Root and Major 3rd (C2-E2): A solid C major foundation.
• Major 7th (B2): Adds a sophisticated Cmaj7 flavor.
• Major 9th (D3): Further extends the chord to Cmaj9.
• Major 13th (A3): Completes the Cmaj13 voicing, giving it a full, open character.
• Octave Major 3rd (E4): Reinforces the major quality.

How to Tune

This tuning involves significant downtuning for most strings from standard E Standard (E-A-D-G-B-E). Please proceed with caution, especially with larger semitone movements, as string tension will be significantly reduced. For movements exceeding 4 semitones, consider using a heavier gauge string to maintain playability and intonation.

• 6th String (Low E): From standard E2, tune down 4 semitones to C2. (Caution advised: -4 semitones)
• 5th String (A): From standard A2, tune down 5 semitones to E2. (Heavier gauge string recommended: -5 semitones)
• 4th String (D): From standard D3, tune down 3 semitones to B2. (Caution advised: -3 semitones)
• 3rd String (G): From standard G3, tune down 5 semitones to D3. (Heavier gauge string recommended: -5 semitones)
• 2nd String (B): From standard B3, tune down 2 semitones to A3. (Normal range: -2 semitones)
• 1st String (High E): Keep as is; no change (0 semitones). The E4 remains E4.

String 6 (lowest): C2
String 5: E2
String 4: B2
String 3: D3
String 2: A3
String 1 (highest): E4