1st recorded trk sound changes when trying to record 2nd trk

I'm trying to record 1st track with bassline sound, then the second sound with a snare drum sound. How do I keep the bassline sound locked in from changing to the snare drum sound. I'm working with a mpc2000xl and roland xp-60. I'm in the performance mode on the roland and set as slave, using the handshake method on the midi cables. Mpc is set to midi device 1 track 1 pgm off, track 2 device 2 for 2nd track.

change the MIDI selection, you have 16 for each line

I tried changing the midi selection and it did not work either. (example) track one midi 1A-device 01, track two midi 2A-device 02. What else could it be.

Is the snare from a MIDI source or from a drum bank in the MPC? If it's from a drum bank, keep the bass on MIDI device 1 and have the snare on Drum and whatever program it's in. If it's all from the Roland than you have to set it to multi-timbral mode so when you switch to device 2, the bass is saved on the first channel and you can play something on the second channel. Hope this helps, peace.