sounds are changing on me..using akai mpc 2000 professional

can someone please help me?....i have the yamaha s30 keyboard and when i go to record sounds into the akai from the keyboard..and i go to change instruments on the keyboard the whole beat changes on the akai.. can someone please tell me why its doing this and what i can do to fix it?
and does anyone know where i can get sounds for the akai mpc 2000 professional?

change the track on the mp before you do the keyboard

the last advice did not work for me... i tried changing the track first on the mpc and my whole sound still changes when i go to the next sound...can anyone else help me out?

did you press stop first??

yes i pressed stop first... but they are still changing

go to the midi page, and for the sampler disable receive program change.