Split mean "Share". This is a changer action that allows to obtain an "in tune" middle note" when 2 actions pedal and knee are engage on the same string. in this case alteration is shared between pedal and knee action.
For exemple (E9 emmons setup), string 5 give a B open string.
With A engage we go from B to C#.
With X knee engage we lower B to Bb.
When we engage pedal A and knee X together we obtain a middle note between C# and Bb.
Our goal is to obtain a C with A and X engage (Then with A,B and X engage we can get a minor chord).
NB: Some call Knee "X" with the letter "V" (knee or lever V).
1. Split tuning with allen screw behind the changer
1. Locate the split screw (allen screw) located behind the changer (some are taped for all strings others have only few holes for split screws). The backing movement of the changer arm is now limited by the split screw.
2. Tune the open string.
3. Engage the pedal and tune the raise with the nylon tuning.
4. Engage pedal end Knee and tune the lower with the nylon tuning.
5. Engage the knee (only) and adjust with the split tuning screw.
2. Using an extra Pull rod (Carter, Mullen before G2, MSA...)
Changer Arm Backing movement is limited by the Raise Finger that does not go against the internal stop changer but against the nylon screw of an additional rod (extra rod). This tunable extra rod is here to adjust lower action (knee action).
1. Tune string 5 (open string)
2. Tune the raise with pedal engaged (with his nylon tuning)
3. Tune the split lower (pedal and knee engaged) with the Lower finger's nylon tuning
4. Tune the Final lower (knee engaged, no pedal) with the colored raise nylon (in red)