Does anyone know how these two files differ?

The reason I ask is that I have downloaded a song from the net. It played fine through the computers audio in PT, but when I redirected the output to my Yamaha keyboard, the drums came out as a very dodgy piano sounding track.

I renamed the song to a .mid rather than a .kar, & while the lyrics are now hard to read on the screen, the drum output is now drums.

If I rename the file back to .kar to make it easier to read lyrics, the drums go back to piano.

Anyone got any ideas?