instruments: document midi bug

templates/predefined-instruments/README.md

@@ -56,5 +56,8 @@ mind and want to use a different naming, you can just change
 the names in `mystaffnames.ily` and all your scores that
 `\include` this file will be affected!
 
+**Known issues:** custom contexts don't work with MIDI (ugh!!).
+See `midi-bug.ly`.
+
 Note: as of 2013-09-06, this is still in very early stage
 of development.

templates/predefined-instruments/midi-bug.ly

@@ -0,0 +1,47 @@
+\version "2.16.2"
+
+\markup \justify {
+  Below i've defined custom contexts: SopranoStaff and SopranoVoice.
+  However, they don't work with midi - first i get a
+  \typewriter "warning: cannot find or create new `SopranoVoice'"
+  and ten "\lyricsto" fails, saying that it \typewriter "cannot find Voice `sop'".
+  I suppose that because of some Midi bug a Voice is created instead of
+  SopranoVoice, and then "\lyricsto" cannot find the SopranoVoice
+  it is supposed to find.
+
+  Without "\midi" block eveerything works fine.
+}
+
+\layout {
+  \context {
+    \ChoirStaff
+    \accepts "SopranoStaff"
+  }
+
+  \context {
+    \Staff
+    \type "Engraver_group"
+    \name "SopranoStaff"
+    \alias "Staff"
+
+    \accepts "SopranoVoice"
+    \defaultchild "SopranoVoice"
+
+    instrumentName = "Soprano"
+  }
+
+  \context {
+    \Voice
+    \name "SopranoVoice"
+    \alias "Voice"
+  }
+}
+
+\score {
+  <<
+    \new SopranoVoice = sop { c' b' a' f' }
+    \new Lyrics \lyricsto sop \lyricmode { la la la la }
+  >>
+  \layout {  }
+  \midi { }
+}