using midi cable with Nord stage 88 EX

hi.
i use cubase 6 32 bit, with m audio fast track pro,
when i record midi from my nord (with midi cable)
it records the events, but when i play it again through the nord i hear the piano, but also another level of
strings or something, not exactly sure what it is…
anyone knows what it means and how do i get rid of it???
cheers…
itai.