This unique tuning, originally named "Drop C With Major Third Subset", is designed for a 7-string guitar, offering a complex yet highly functional soundscape. It's crafted to enhance fretboard access, particularly through its innovative 'Major Thirds set' across the higher strings.

The tuning is noted by its creator to be similar to "Old Man Gloom A#", building upon that foundation with an extended set of Major Third intervals. This suggests a tuning well-suited for heavy, resonant tones often found in genres demanding rich harmonic depth and efficient chord voicings.

Technical Analysis of Open Strings:

The open string notes from the lowest (String 7) to the highest (String 1) are: A#2, F2, A#3, D3, F#4, A#4, D4.

• String 7 (A#2): Provides a deep, resonant low end, establishing an A# (Bb) foundation.
• String 6 (F2): Surprisingly, this string is tuned 5 semitones lower than String 7, making it the absolute lowest note of the tuning. This creates an immediate open Perfect Fourth (F-A#) interval with String 7.
• String 5 (A#3): Jumps a significant 17 semitones (an octave and a Major Third) from String 6 (F2). This wide interval creates unique possibilities for arpeggios and voicings that are challenging in standard tunings.
• String 4 (D3): Drops 9 semitones (a Major Sixth) from String 5. This string marks the beginning of the 'Major Thirds set' and establishes the D root.
• String 3 (F#4): Tuned 14 semitones higher than String 4 (an octave and a Major Third), maintaining the D-F# Major Third relationship.
• String 2 (A#4): A direct Major Third (4 semitones) above String 3 (F#4), completing the D-F#-A# triad.
• String 1 (D4): Tuned 9 semitones lower (a Major Sixth) from String 2, bringing the D root back an octave higher than String 4. This string, mentioned as "added D4" in the original description, effectively reinforces the D Major triad.

Chordal and Fretboard Access Analysis:

• D Major Triad Core: The most prominent feature is the collective D Major Triad (D, F#, A#) across strings 4, 3, 2, and 1 (D3, F#4, A#4, D4). This setup makes playing D Major chords, arpeggios, and melodies in D Major incredibly intuitive and accessible across the higher register. The presence of the D root on both S4 and S1 provides versatility for voicings.
• Low-End Power: The combination of F2 and A#2 (Bb2) on strings 6 and 7 offers a dark, thick foundation, ideal for powerful, resonant open fifths, fourths, or dissonant low-end chords. This low F and A# could imply a strong Bb major or F minor/major tonality.
• Complex Harmony: The full open tuning comprises the notes F, A#, D, F#. This creates a rich, ambiguous harmony that can lean towards a D Augmented triad with an added F, or various extended Bb/F chords. This complexity encourages creative chord discovery.
• Unique Voicings: The unconventional and large interval jumps (e.g., S6 to S5, S5 to S4, S2 to S1) between certain strings will naturally lead to unique chord voicings and scale patterns that are not possible or are difficult to achieve in standard tunings. This encourages exploration beyond conventional shapes.
• Fretboard Efficiency: The 'Major Thirds set' starting from String 4 provides a consistent interval pattern across these strings, which can simplify the memorization and execution of scales, arpeggios, and chord shapes within that section of the fretboard, as fingerings can be moved laterally with ease.

Overall, the "Bb Power D Major Stacks (7-String)" tuning is an advanced and highly specialized setup, rewarding players who seek a powerful low end combined with clear, accessible Major Third voicings in the higher register. It provides a distinct sonic signature for genres ranging from heavy metal and progressive rock to experimental and jazz fusion.

Open String Notes:

• String 7 (Lowest String): A#2
• String 6: F2
• String 5: A#3
• String 4: D3
• String 3: F#4
• String 2: A#4
• String 1 (Highest String): D4

How to Tune:

To tune your 7-string guitar to 'Bb Power D Major Stacks', adjust each string from its current state as follows:

• String 7 (A#2): Tune down 1 semitone to reach A#2.
• String 6 (F2): Tune up 1 semitone to reach F2.
• String 5 (A#3): Tune up 1 semitone to reach A#3.
• String 4 (D3): Keep as is; no change (0 semitones) to remain at D3.
• String 3 (F#4): Tune down 1 semitone to reach F#4.
• String 2 (A#4): Tune down 1 semitone to reach A#4.
• String 1 (D4): Tune down 2 semitones to reach D4.

Please note that none of the individual string adjustments exceed a change of 4 semitones, so a different string gauge is generally not advised solely based on these movements, assuming your current strings are appropriate for your instrument.