Here's what GROK had to say about tuning 'split tuning'.

[Michael Lester]

I recently acquired a Mullen D10 RP with split tuning on 2. Never had this feature before, Changing strings last night really confused my in line tuner. In fact, I didn't even know that this guitar had split tuning on it.
I queried GROK -
Is this info accurate? Wow! What evil genius came up with this. Had to come from lab like in 'Young Frankenstein'.

Tuning "split tuning" on a pedal steel guitar refers to adjusting the mechanical splits (often involving splitter rods, nylon nuts, or set screws) that allow certain strings to achieve an intermediate or "split" note when combining a raise (from a pedal) and a lower (from a knee lever). This is common on setups like E9th tuning, enabling nuanced pitch changes (e.g., B to Bb to C on strings like 5 and 10). The exact process can vary by guitar model (e.g., Williams, ZumSteel, or universals), but it generally follows a sequence after basic setup and open-string tuning. Always use a reliable tuner or reference pitches, and note that factory settings are often pre-tuned—make small adjustments to avoid detuning other aspects.General Prerequisites Ensure the guitar is assembled: Legs attached, pedal bar secured, pedal rods connected (often numbered for ease).
Tune the open strings first (e.g., for 10-string E9: F#, Eb, G#, E, B, G#, F#, E, D, B from strings 1-10).
Tune individual pedals and knee levers: Engage each, locate the adjustment nut (e.g., hex or nylon in the changer window), and match the target pitch while pumped/engaged.

Step-by-Step Tuning Process for SplitsThis draws from standard methods for guitars with splitter features (optional on some models for strings like 5, 6, 10). If your guitar has splitter rods, install them first (thread through raise hole on changer lever, hook to knee lever bell crank, add spacer and hex nut).Tune the Open and Individual Changes:Tune the string to its open pitch using the main tuning keys.
Engage the raise function (e.g., Pedal 1 or 2) and tune the raised note (e.g., B to C# on string 5) using the nylon or hex nut in the changer.
Engage the lower function (e.g., vertical knee lever, VKL) and tune the lowered note (e.g., B to Bb) initially if needed, but final adjustments come later.

Engage Both Raise and Lower for the Split Note:Simultaneously engage the raise pedal and lower knee lever (e.g., Pedal 1 + VKL for string 5, producing a middle C from the combined B to C# raise and B to Bb lower).
Pick the string and listen for the resultant "middle" or split note (e.g., C).
Adjust this split note to pitch using the lowering rod's hex or nylon nut (turn clockwise to flatten, counterclockwise to sharpen). On some models like ZumSteel, this is the nylon nut for the lower.

bb.steelguitarforum.com

Fine-Tune the Isolated Lower Note:Release the raise pedal but keep the lower knee lever engaged.
The lowered note (e.g., Bb) may now sound flat or off—adjust it sharp or flat as needed using the set screw at the end of the neck (behind the changer finger for that string) or the splitter rod's hex tuning nut.

bb.steelguitarforum.com +1

Verify against open strings or a tuner (e.g., match the Bb to a reference).

Repeat for Other Strings and Splits:For strings 5 and 10 (B notes): Use Pedal 1 (raise to C#) + VKL (lower to Bb) = split C; tune C with lowering nuts, then isolated Bb with splitter nut.
For strings 6 and 10 (G# notes): Use Pedal 2 (raise to A) + knee lever (lower to F#) = split G; follow the same adjustments.

williamsguitarcompany.com

Common universal split example (e.g., E to Eb on strings 4/8): After open tuning, lower E's to Eb with nylon tuners, engage the 6th pedal, and tune the 4th string's nylon tuner to pull back to E. This may affect lever holds.

bb.steelguitarforum.com

Tips and TroubleshootingUse "sweetened" tuning if applicable (slight offsets for better chord intonation), but check for sharpness (e.g., 45% sharp on combined RKL + B pedal) and adjust nuts accordingly.

thebritishsteeliessociety.co.uk

For mechanical setup: Ensure the splitter engages precisely (e.g., 9th string nut engages at D on 2nd string).

mobile.steelguitarforum.com

If notes detune when combining, revisit the middle note adjustment—small turns are key.
Models differ: Consult your guitar's manual (e.g., Williams for hex nuts, Zum for nylons). If issues persist, professional setup or videos demonstrating the changer window adjustments can help.
Practice chiming harmonics or using a strobe tuner for precision, especially on extended tunings like C6 or D13 where splits might be customized (e.g., D to Db half-stops on 4th string).

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This setup enhances playability for licks and chords, but start slow to avoid over-adjusting. If your guitar lacks splits or uses a different copedent (pedal/lever chart), the process may not apply directly.

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Explain sweetened tuning offsets

[Tucker Jackson]

What a load of absolute AI garbage. Aside from being difficult to understand, it's wrong.

The procedure for tuning a split is NOT obvious for two reasons:
1) You tune the split note before you tune the regular lower.

2) The nuts you use to tune both of these are the opposite of what logic would dictate. As Fred Treece has pointed out, this confusion partially stems from the unfortunate naming convention where we call something a 'splitter screw' (or the splitter hex nut).... but that's not the one we use when tuning the split! We use the regular lowering hex nut to tune the split.

We'll use an example of the 6th string that's setup to split to a G note, but the concept is the same for a split on any other string:

The B-pedal raises the string to G# as normal. A knee lever lowers the 6th string to F#... and if you engage both of those together, you get the split note of G. It will be a little out of tune unless your guitar is set up for split tuning. This is achieved with either an extra pull rod, or some guitars have special screws in the back of the changer housing.

The order of tuning matters here, since one step builds on the previous one

1) Get the open string tuned to G# at the keyhead.

2) Tune B-pedal RAISE to the A note using hex nut.

3) This step is counterintuitive: next we tune the SPLIT to the G note (rather than the simple lower to F#).
Engage both the B-pedal and the knee lever to tune the 'split' to the G note.

Use the hex nut at the bottom of the changer (the section for doing lowers, closest to the floor) for getting the SPLIT to the G Note in tune. Using this nut -- the one we would normally use to tune a regular lower of the 6th string if there were no split -- is counterintuitive, but it's correct when there is a split installed on the guitar.

4) Tune the regular lower to F# as the last step -- and you'll use a special hex nut or screw in the changer to make the minor adjustment to get up to the target pitch. Some people call this the "splitter nut" or "splitter screw," but as you see, this is a misleading name since we're not using it to tune the split note. We've already done that. We're using it to make a micro-adjustment to dial in the "final lower" pitch of this string to F#.

* If your guitar uses the extra rod method: use the hex nut in the top raise section of the changer for 6th-string (i.e., next to where the B-pedal hex nut does its thing) to bring the pitch back up slighty to hit your target F# note. Sometimes, this hex nut is a different color so you'll know what it's for.

* If your guitar uses a screw on the back of the changer method: turn the screw clockwise to bring the pitch back up slighty to hit your target F# note.

[David Wren]

Folks need to realize that "AI" doesn't really know the answers to your questions, but rather it is a very quick "regurgitation" of other internet posts on your subject.

Keeping this in mind, re-read the previous post... sound like a compilation of what folks might say on this forum

BTW, I hate "AI"

But... I love split tuning

[Michael Lester]

Thank you sincerely Tucker... your explanation made a difference and is very helpful.

As to Ai, I ended up at Grok because there is a thousand mentions of 'split-tuning' on a casual search - but it's very confusing. For me, it's like the refrigerator repairman explaining how a refrigerator makes things cold. My eyes glaze over pretty quickly.

On the upside, I guarantee that future inquiries of Ai WILL show Tucker's explanation just because it is posted here on the Forum.

[David Wren]

Micheal, the websites for at least MSA and Williams Guitar Company have easy to understand instructions for split tunings.. so you might check those out. Mickey Adams also has a nice, easy to understand you tube video on the subject.

Once you get used to using split tuning, you will appreciate what it can add.... I would suggest starting with your "X" lever (B-> Bb).... going from A pedal on C#, then A pedal plus X lever, then open B, and finally X lever down to Bb... it's very smooth

Hope this helps.