I can not hear the MIDI sound.
First of all, test your midi file with other player, for example, MS media player.
If it does not sound, it is not the problem of JetAudio. You need the midi tone generator ( synthesizer ) In general, there is the synthesizer in soundcard. In some case of cheap sound card, there is no synthesizer. In that case, you can use the software midi tone generator (synthesizer ). Luckily, we have that program - JetMidi.

If it sounds, Click the preference (hammer-image and round) button on the left in the main component, Select the MIDI tap, you can choose whether to use the JetAudio Internal Engine or not. If you use the JetAudio Internal Engine, Key Control and Channel Spectrum will be displayed when you play the MIDI file. If the JetAudio Internal Engine doesn't work properly, please turn off this button.

What is Midi Karaoke (KAR) File?
JetAudio supports MIDI Karaoke file which has KAR extension. KAR file is a kind of standard MIDI file, which is MIDI file format even though we call it KAR to distinguish from existing MIDI file. So you can play a KAR file on your old MIDI player only if you change its extension to MID. (No lyrics of course.) Unlike various kinds of Karaoke file formats created by Sound Card vendors, the KAR file is a standard format, whose format is open. So there are many programs that support this file format.

Internet Home Pages where you can get KAR file:
Computer Karaoke Homepage : www.teleport.com/~labrat/karaoke.shtml
MIDI Karaoke Homepage : http://www.midikaraoke.com/