While working with a much larger version of the score below (BWV 206 chorale in 4 voices), I tried using the NoteNames engraver to put note names under each voice. For some reason, invoking it twice causes the clef and instrument name to change on the top staff. The notes (and the note names) are correct, but the Soprano line gets a bass clef and the bass instrument name. Is this a known problem?
Thanks,
Mike
\version "2.12.3"
ASvoiceAA = \relative c'{
\set Staff.instrumentName = #"Soprano"
\clef treble
\key f \major
\time 4/4
\partial 4
a'4 bes a g d' | % 1
}% end of last bar in partorvoice
ABvoiceDA = \relative c{
\set Staff.instrumentName = #"Bass"
\clef bass
\key f \major
\time 4/4
\partial 4
d4 g a bes a8 g | % 1
}% end of last bar in partorvoice
\score {
<<
\context Voice = ASvoiceAA { \ASvoiceAA }
\context NoteNames = NNS \ASvoiceAA
\context Voice = ABvoiceDA \ABvoiceDA
%% ok.png when line below commented out. withbug.png if left in.
\context NoteNames = NNB \ABvoiceDA
>>
}%% end of score-block
ok.png