George,
I do know a software that allows you to remove, replace, mute...
any instrument in a Midi File, it's call Karawin. This software is the first Karaoke for Midi Karaoke, it will open the Midi & Kar and will also play the mp3 karaoke and standard mp3 files.
You may want to try it, it's a Shareware software and I'm sure you'll be interrrested to buy the license.
Anything you see on the market is a copy, it's available in many language.
www.karawin.com
The difference between those Midi Karaoke player & Roland Canvas is Roland uses it's own driver for sequencer versus the other wich you need to use the sequencer in your audio card.
You will not get a good result if you dont have a good card.
By default, it will play using the Midi mapper, you need to change it to SB Midi synth A or B if you have a Sound Blaster. Karawin will also allow you to ad reverb on your music, important with Midi file.
Please, let me know if this helps you.
Regards