This question might have been better posted in the NMRPipe group.

Normally, in NMRPipe, gradient enhanced Varian 2D data is converted with "-yMODE Rance-Kay". This actually runs an NMRPipe macro to perform gradient shuffling of pairs of adjacent 1D vectors during the conversion, but it is run "in background", and you don't see it explicitly:

| nmrPipe -fn MAC -macro $NMRTXT/var_ranceY.M -noRd -noWr \

In an interleaved version of the gradient-enhanced data, there are two possible formats. In the case array="phase,IPAP", the innermost acquisition loop is the Rance-Kay phase encoding. So, adjacent pairs of vectors are Rance-Kay pairs, and you can convert this data with "-yMODE Rance-Kay". Then, later processing steps can use COADD to select or combine channels.

However, when array='IPAP,phase' the IP/AP alternation is in the innermost acquisition loop. This means that manipulation with COADD must happen before gradient shuffling. In these cases, we convert with "-yMODE Complex", and then explicitly include gradient shuffling just afterwards, for example:

nmrPipe -in test.fid \
| nmrPipe -fn COADD -cList 1 -1 -time -axis Y \
| nmrPipe -fn MAC -macro $NMRTXT/var_ranceY.M -noRd -noWr \
| nmrPipe -fn SOL \
| nmrPipe -fn SP -off 0.5   ... etc ....
  -out dif.ft2

Also, one more tip:

When dealing with this kind of data, it can be handy to extract the IP and AP channels separately ("COADD -cList 1 0" and "COADD -cList 0 1") so that they can be inspected first to find the optimum coefficient for cancelation of IP and AP signals. Then, use the stand-alone program "addNMR" to combine the two channels to form scaled sum and difference, for example:

addNMR -in1 A.dat -in2 B.dat -c1 1.0 -c2 1.2 -out sum.dat -add
addNMR -in1 A.dat -in2 B.dat -c2 1.0 -c2 1.2 -out dif.dat -sub

I found a post post from Frank Delaglio on the NMRPipe message board that answers the same question, but I think there was a confusion about ordering of the IP/AP loop with respect to the quadrature frequency discrimination loop.

This solution worked for the setup where array='IPAP,phase'. For the opposite setup, try Frank's post.

The usual 2D conversion script (but notice the -xMODE and -yMODE setup - both must be Complex) and the point count includes both IP and AP sub-experiments:

#!/bin/csh

var2pipe -in ./fid -noaswap  \
  -xN              1280  -yN               400  \
  -xT               640  -yT               200  \
  -xMODE        Complex  -yMODE        Complex \
  -xSW        10002.501  -ySW         2800.000  \
  -xOBS         799.805  -yOBS          81.053  \
  -xCAR           4.754  -yCAR         118.618  \
  -xLAB              H1  -yLAB             N15  \
  -ndim               2  -aq2D          States \
  -out ./test.fid -verb -ov

sleep 5

To process the data you can use that same method that is normally used to process HSQC, but with one line inserted right after TP (transpose) command with the contents | nmrPipe -fn COADD -cList 1 0 -time \

... first obtain one subset:

nmrPipe -in test.fid \
... process X dimension, usual way no Rance-Kay for gNhsqc_IPAP ...
| nmrPipe -fn TP \
| nmrPipe -fn COADD -cList 1 0 -time \
...
-verb -ov -out A.ft2

... then change the COADD line and obtain the second subset, like so:

nmrPipe -in test.fid \
....
| nmrPipe -fn TP \
| nmrPipe -fn COADD -cList 0 1 -time \
....
-verb -ov -out B.ft2

Then calculate the final separated spectra.

addNMR -in1 A.ft2 -in2 B.ft2 -out A+B.ft2 -c1 1.0 -c2 1.25 -add
addNMR -in1 A.ft2 -in2 B.ft2 -out A-B.ft2 -c1 1.0 -c2 1.25 -sub