This is probably due to your MIDI sound card; the way MIDI music works is that the songs we supply consist of "instructions" to the sound card that are sort of like a player piano — they say things like "using a piano instrument, play the note C... now play F-sharp on a trombone..."

The result of this is that the music can sound totally different on different computers. Your "piano" might not sound like another at all, and we've heard some sound cards where a few instruments are just awful — for example, any tune that uses a "trombone" might be intolerable.

Short of buying a new sound card, there isn't much that can be done to directly fix it, but you can definitely minimize the annoyance.

The best thing to do is visit Web sites that have more MIDI files, and add new songs that will perhaps sound better on your sound card.

 
See also:
How do I download and add free music to Holiday Lights for Windows?
Why can't I hear any music?