piano voice needs to be channel 1

I have a pnomation piano player system. In order for it to work the piano must be channel 1. When I download midi files for songs where the main instrument is not piano, I have to change the instrument to piano, but the piano must be channel 1. How can I force all notes to be piano on channel 1? Please Help! I am converting midi file hymns so they will play on my player piano. Some of these hymns are written for organ on a different channel than 1, so just changing the voice to piano doesn't work. You must also change the channel to 1, but I don't know how.