MIDI novice; cannot get Reference examples to play

[ivan . k . kuznetsov]

I am _absolutely new to MIDI.  I am however
able to get some random MIDI files I found on the
web to play through my Alesis synthesizer with
the command:

    aplaymidi --port 16:0  file_i_found.mid

(I am working under Linux, CentOS 5.6).

However, I cannot get any Lilypond created midi
files to play with the above syntax.  The command
will execute, but _no_ sound is produced by my
synthesizer.

Specifically, I am trying the examples from
the Lilypond Reference  3.5.1 and 3.5.5 to
play.  The .midi files are created without error,
the "aplaymidi" command executes, but there
is no sound.

Can anyone suggest what I can do to remedy
this situation?  Thanks again.