Problem with kick drum sound

[Dan]

I programmed a kick drum that sounds great when it's played alone, but it gets higher pitched when I combine it with the rest of the sounds in the multi. I know it's not a polyphony issue because I only have three other patches and I turned unison mode off on all of them. The strange thing is that if I mute out all the other patches except for the kick drum, it still sounds weird for one more kick and then goes back to normal. I have a Virus b. Any ideas?

Thanks,
Dan