Track doubling

[Lacidar]

I have a QS7 which I enjoy using. My question is, why when I double a
drum track, the two track when played together seems to phase given a
sort of flange or distorted unwanted sound on the QS7?

The reason I need to solve this problem is because when I was at school
studying to be Sound Designer I use the lab to create some music using a
midi sequencer. Most of my midi files have the drum track doubled and
some even tripled to give a nice punchier sound. The sound I get at the
lab at school sound great which I was using an Roland XP10 much cheaper
than the QS7 but not as good.

I would like to be able to just load my midi files in my sequencer and
play my QS7 the way I use to play at school in the lab. There the
sequencer was Performer on a apple computer, right now I am using a pc
with Midisoft Studio 4 sequencer. I was wondering if it's the sequencer
that is not setup right.

Can anyone point me in the right direction?

Thank you in advance.