Timothy Lanfear supplied a simple
understandable way of achieving my aims.
However on reflection there is a drawback;
the midi output is not correct. Two identical midi outputs
with the same name are produced but share the same midi
instrument
The example I posted does produce a midi file with both bassoon and
clarinet. Here is the terminal output from timidity.
timidity tmp.midi
Requested buffer size 32768, fragment size 8192
ALSA pcm 'default' set buffer size 32768, period size 8192 bytes
Playing tmp.midi
MIDI file: tmp.midi
Format: 1 Tracks: 3 Divisions: 384
Sequence:
Text: creator:
Text: GNU LilyPond 2.19.56
Instrument: bassoon
Instrument: clarinet
Playing time: ~12 seconds
Notes cut: 0
Notes lost totally: 0