I'm not familiar with the partcombiner, though, below a very bad
workaround, found deep, deep in the quick n' dirty junk room.
#(define-music-function (ctx-name mus)(string? ly:music?)
#{ << $mus \context Voice = $ctx-name \grace s2\! >> #})
endI = \terminateHairpin "one" \etc
endII = \terminateHairpin "two" \etc
\new Staff \partcombineII \musicA \musicB
I have tried your solution to Kieran’s recent problem with \partcombine, but didn’t manage to find the \partcombineII that you use - I hope it isn’t a stupid question, but where is this to found?
Many thanks - as I’m sure I shall need it too sometime.