There are various concepts of tuning the four additional bass strings. Maestro Yepes tuned the four additional bass strings in descending whole steps, supplying the necessary sympathetic resonance to further complete the overtone series of each half step on the guitar.
Narciso Yepes Tuning:
7TH string C (octave lower than C on 3rd fret, 5th string)
8th stringBb (re-entry)
9TH stringAb (down a whole step)
10th string Gb (down a whole step)
For example, if you play a G on the third fret of the 1st string of a six string guitar you have a certain length of sustain because there is an open G string to sympathize with that tone. If you play the F# on the second fret of the first stringE , there is less sustain because there is no sympathetic string tuned to that pitch. Therefore, there are four missing sympathetic resonances on the six string guitar. If you play a C,Bb, Ab, and Gb on the first string E, there will be less sustain from these notes than the others because there are no sympathetic resonant strings. This was Maestro Yepes primary reason for conceiving the ten-string guitar. By adding these pitches in four extra bass strings, now provides each half step with the sympathetic resonance making a more physically completed instrument. Referred to as Baroque Tuning :
7th string D
8th string C
9th string B
10th string A
This is another arrangement of bass strings used by some players for the benefit of playing music from the Baroque era.
Definition of the Marlow Method Tunings for Ten-String Guitar
by Steven Bastien
All Marlow tuning methods use a standard guitar tuning on string 1 through 6.
The 7-th string is up a fifth (inverted fourth) to create a reentrant tuning. The remaining 3 strings then typically decend in fourths.
Marlow tunings can be defined by three traits: (i) strings 1-6 are in standard tuning, (ii) all strings are related by perfect fourths (or one augmented fourth may be present), and (iii) a one octave reentrance is placed between the 7'th and 6-th string. A corollary of the definition is that all 7 wound strings (4-10) cover all notes of a major scale.
This definition results in 5 possible tunings.
2. The standard "Marlow Alternate Tuning" is also a reentrant tuning in fourths, however
the interval from the 8'th to 7'th string is an augmented fourth as follows;
(note that this tuning provides all notes of the C major scale on the wound bass strings).
E B G D A E B F# C# G#
E B G D A E B F C G
3. The "Marlow D Tuning" requires that the open strings be in the Marlow Method
tuning, with the exception that the 10'th string is tuned to G as follows.
E B G D A E B F# C# G
1. The standard "Marlow Method Tuning" is a reentrant tuning in all perfect fourths as follows:
(note that this tuning provides all notes of the A major scale on the wound bass strings.)
4. The "Marlow G Tuning" requires that the open strings be in the Marlow Method
tuning, with the exception that the 10'th string is tuned to G and 9'th to C as follows.
E B G D A E B F# C G
5. The "Marlow F Tuning" requires that the open strings be in the Marlow Method
tuning, with the exception that the 7'th string is tuned to Bb as follows.
E B G D A E Bb F C G