missing midi-file

[Thomas Morley]

With the following code LilyPond creates 4 midi-files, but two of them
are named identical, overriding each other. So finally only three
midi-files are present.

\version "2.19.48"

\book {
  \score { { c'4 }  \midi {} }
  \score { { cis'4 } \midi {} }
}

\book {
  \score { { d'4 } \midi {} }
  \score { { dis'4 } \midi {} }
}

Output from terminal:

GNU LilyPond 2.19.49
Processing `missing-midi.ly'
Parsing...
Interpreting music...
Interpreting music...
MIDI output to `missing-midi.midi'...
MIDI output to `missing-midi-1.midi'...
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Interpreting music...
Interpreting music...
MIDI output to `missing-midi-1.midi'...
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
MIDI output to `missing-midi-1-1.midi'...
Success: compilation successfully completed

The problem is located in `write-performances-midis' from midi.scm.
The naming-procedure is insufficient for the above use-case.


I stumbled across it while researching a method to set custom names
for midi-files, which is a valid feature-request on its own.
See discussion starting here:
http://lists.gnu.org/archive/html/lilypond-user/2016-09/msg00718.html

Cheers,
  Harm