Midi - Can't Turn Off Generic Piano Sound

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Hi,
I'm new to LMMS but really liking it so far. However, I'm having a problem getting rid of a generic piano sound from my midi keyboard. I can activate VSTi's which sound great, but whatever I do I still get a piano sound similtaneously. If I mute everything it's still there, so I can't isolate any sounds from this. Any ideas? LMMS isn't picking up other PC sounds, so it's definately being generated within the program.
Thanks.
Solved it - I had my soundcard ticked as a midi output.